(CNN)Secretary of State John Kerry credited diplomatic strength and newly developed ties with Iran in helping secure the quick and safe release of 10 American sailors Wednesday.
"These are always situations as everybody here knows which have an ability, if not properly guided, to get out of control," Kerry said in a speech at the National Defense University. "I'm appreciative for the quick and appropriate response of the Iranian authorities."
He said that "all indications suggest or tell us that our sailors were well taken care of, provided with blankets and food and assisted with their return to the fleet earlier today."
The sailors were released Wednesday to the American naval fleet in the Persian Gulf after being captured by the Iranian Revolutionary Guard Tuesday.
READ: Former Navy commander: Ships in Iran's waters 'a severe failure'
Kerry said things might not have gone as smoothly before the U.S. opened dialogue with the country over its nuclear program, culminating in a deal to curb its operations reached between Iran and the U.S. along with five other world powers in July.
"I think we can all imagine how a similar situation might have played out three or four years ago," Kerry said. "In fact, it is clear that today this kind of issue was able to be peacefully resolved and efficiently resolved and that is a testament to the critical role that diplomacy plays in keeping our country safe, secure and strong."
Video shows U.S. sailors' capture
Video shows U.S. sailors' capture 02:37
But critics of the administration take issue with its characterization, and have slammed the White House for the incident and questioned its timing. The seizure of the sailors came days before the nuclear deal is expected to go into force and sanctions on Tehran -- which will be lifted in exchange for Iran's freeze on its nuclear nuclear program -- are set to start being rolled back.
The capture of the Navy sailors was quickly seized on by U.S. opponents of the nuclear deal as the latest in a series of provocations by Tehran since the deal was agreed, which include aggressive attempts to wield power in its immediate neighborhood and ballistic missile tests that the United Nations charged violated a Security Council resolution.
CNN obtained video of the sailors being captured Tuesday, showing them with their hands on their heads and on their knees.
"This kind of openly hostile action is not surprising. It's exactly what I and so many others predicted when President Obama was negotiating the nuclear deal with Iran -- that it would embolden their aggression towards the United States and our allies in the region," Arkansas Republican Sen. Tom Cotton told Wolf Blitzer on "The Situation Room" on Tuesday.
Other Republicans said the release of the video was a further rebuttal of the Obama administration's attempts to play down the incident.
"It's horrible. This is not what friendly nations do, especially if this was about a mechanical failure. You don't detain a friendly neighbor or friendly nation's armed forces and detain them overnight when you have friendly relations," Rep. Patrick McHenry, a North Carolina Republican, said on CNN's "Legal View" Wednesday.
Was there an apology?
Even with the release of the sailors, questions still remained, including whether the sailors or any U.S. officials apologized for the incident.
Iranian authorities let the sailors go after determining that their vessels' entry into Iranian waters was unintentional and "after they extended an apology," according to a statement from Iran's Revolutionary Guards Corps, quoted in the country's semi-official FARS News Agency. The statement went on to say, "The Americans have undertaken vnot to repeat such mistakes."
But the State Department quickly rebutted that report Wednesday morning.
"There is no truth in reporting that Secretary Kerry apologized to the Iranians," Kerry spokesman John Kirby told reporters Wednesday, later tweeting that the claim had "zero" validity. "As the Secretary said in his statement this morning, he expressed gratitude to Iranian authorities for their cooperation in swiftly resolving this matter, and noted that the peaceful and efficient resolution of this issue is a testament to the critical role diplomacy plays in keeping our country safe, secure, and strong."
Iranian Foreign Minister Javad Zarif, who has maintained open lines with Kerry and U.S. officials, made no mention of an apology in a tweet he sent after the sailors were released.
"Happy to see dialog and respect, not threats and impetuousness, swiftly resolved the #sailors episode. Let's learn from this latest example," Zarif wrote.
A Navy statement said the detained sailor have been transferred to shore and are no longer on USS Anzio, which helped carry them back to U.S. custody.
The sailors were captured Tuesday after their two naval boats entered Iranian waters near Farsi Island, in the Persian Gulf.
The wait for the sailors' release Wednesday morning dragged on for hours, with Iranian officials interrogating the sailors about their motives and demanding a U.S. apology.
But an Iranian Revolutionary Guard Corps spokesman told state-run media the boats strayed into Iranian waters by accident.
"The evidence suggests that they unintentionally entered the Iranian waters because of the failure of their navigational system," IRGC spokesman Ramazan Sharif said.
On Wednesday afternoon, the sailors traveled on their two boats to a rendezvous point in the Persian Gulf, a U.S. official said. They were escorted by Iranian boats, which turned back when they reached the rendezvous point in international waters.
The sailors then boarded the guided missile cruiser USS Anzio, where they underwent medical checks Wednesday.
"There are no indications that the Sailors were harmed during their brief detention," the U.S. Navy said in a statement.
The Navy said it would investigate how the sailors ended up in Iranian territory.
Secretary of State John Kerry expressed "gratitude to Iranian authorities for their cooperation in swiftly resolving this matter," in a statement Wednesday.
"As a former Sailor myself, I know the importance of naval presence around the world and the critical work being done by our Navy in the Gulf region," he said, adding later, "That this issue was resolved peacefully and efficiently is a testament to the critical role diplomacy plays in keeping our country safe, secure, and strong."
White House chief of staff Denis McDonough credited Kerry's work opening communications with Zarif through the nuclear deal negotiations with securing the quick release of the sailors.
McDonough said that facts were still being collected and the Navy was investigating the incident, but he said it was too early to make draw other lessons from the incident.
On Wednesday morning, officials interrogated the sailors to see whether they "entered Iranian waters intentionally on an intelligence mission," the IRGC said, according to state-run Press TV.
Iran's foreign minister called for the United States to apologize for the "encroachment" of American vessels into Iranian territorial waters, an Iranian navy official told state-run media.
IRGC Navy commander Adm. Ali Fadavi said the presence of the U.S. Navy in the Persian Gulf waters "disturbed the security of the area" and criticized the U.S. Navy maneuvers.
What the ships were doing
The vessels were en route from Kuwait to Bahrain and were sailing near Farsi Island in the Persian Gulf.
A senior defense official told CNN the boats were in the area of Farsi Island for refueling, but it's not clear whether they actually refueled -- raising the possibility they ran out of fuel.
Another senior defense official said no distress call came from the boats.
Iran's official IRNA news agency reported that the boats were "rescued" by Iranian navy sailors.
There is nothing to indicate the capture was a hostile act on the part of Iran, a senior Obama administration official said.
The upcoming implementation of the nuclear deal might be why the U.S. sailors were held for only one day, a CNN military analyst said.
Senator ties Iran nuclear deal to detained sailors
Senator ties Iran nuclear deal to detained sailors 00:53
"I certainly think they were released quickly because of the ongoing Iran deal," retired Lt. Gen. Mark Hertling said.
Otherwise, "they probably would have been kept a few more days," Hertling said.
He noted that when British sailors were captured by Iran in 2007, they were held for about two weeks.
"I think there potentially is a new age coming about with Iran," Hertling said. "This is going to improve military-military relationships."
In 2004, three British patrol boats were boarded and seized by Iranian security forces in the Shatt al Arab waterway, which divides Iraq and Iran. The crews of the three boats, including eight British sailors and marines, were blindfolded and paraded on Iranian state TV and held captive for three days.
In 2007, Iran captured 15 British sailors and marines in the Persian Gulf and accused them of trespassing in Iranian territorial waters. Britain maintained that its service members never entered Iranian waters.
Those British service members were paraded before then-President Mahmoud Ahmadinejad, and critics said their apologies were extracted under duress. They were released after two weeks.
After the 2007 capture, Adm. Mike Mullen, who was U.S. chief of naval operations at the time, said, "We've got procedures in place which are very much designed to carry out the mission and protect the sailors who are there, and I would not expect any sailors to be able to be seized by the Iranian navy or the Iranian Republican Guard."
CNN's Laura Koran, Jim Acosta, Stephen Collinson, Marilia Brocchetto, Shirzad Bozorgmehr, Sara Mazloumsaki, Elise Labott and Jake Tapper contributed to this report.
Allying against Saudi Arabia?
Facilitate peace talks/aggression from SA?