Ten sailors were detained by Iranian authorities on Tuesday as they sailed from Kuwait to Bahrain aboard two small riverine patrol boats.
We still don't know the reason why the boats were stopped, but Pentagon press secretary Peter Cook says the U.S. has been in touch with the Iranians.
"[Iranian authorities] have informed us of the safety and well-being of our personnel," Cook said. "We have received assurances the sailors will promptly be allowed to continue their journey."
NPR's Tom Bowman reports that the State Department has taken the lead in negotiating with Tehran. Citing a Defense official with knowledge of the situation, Tom reports that Iran says it will release the sailors as day breaks.
The State Department tells NPR's Michele Kelemen that Secretary of State John Kerry has called Iranian Foreign Minister Javad Zarif to discuss the issue.
This is a breaking news story; we'll update this post as soon as we know more.