WASHINGTON - US Secretary of State John Kerry made no expression of regret in his talks with Iran's foreign minister to seek the release of 10 US sailors who were taken into Iranian custody in the Gulf, a US official said on Wednesday.The official, who spoke on condition of anonymity, said there was "no need to express regret" and that Kerry had not done so in several conversations with Iranian Foreign Minister Mohammad Javad Zarif. The Iranian was Kerry's main interlocutor in talks that led to last year's nuclear deal between Iran and major powers.Iran released the sailors on Wednesday after holding them overnight, bringing a swift end to an incident that had rattled nerves days ahead of the expected implementation of the landmark nuclear accord.Iran's Islamic Revolutionary Guard Corps said it had freed the sailors after determining they entered Iranian territorial waters by mistake.The Pentagon confirmed the sailors' safe release but, in a carefully worded statement, it did not explain how they ended up being detained by Iran, saying it would investigate "the circumstances that led to the sailors' presence in Iran."Earlier on Wednesday, US State Department spokesman John Kirby denied reports that Kerry had apologized for the incident. US officials sometimes draw distinctions between an apology and a lesser expression of regret. The US official who spoke on condition of anonymity made clear that neither had occurred.