Officials fear the move could lead to a showdown with the U.S. or other members of a Saudi-led coalition, which is enforcing a naval blockade of Yemen and is conducting its fourth week of airstrikes against the Houthis. 

Iran sent a destroyer and another vessel to waters near Yemen last week but said it was part of a routine counter-piracy mission. 

What’s unusual about the new deployment, which set out this week, is that the Iranians are not trying to conceal it, officials said. Instead, they appear to be trying to “communicate it” to the U.S. and its allies in the Gulf. 

It is not clear what will happen as the convoy comes closer to Yemen. Saudi Arabia has deployed ships around Yemen to enforce the blockade, as has Egypt. An official said the ship convoy could try to land at a port in Aden, which the Houthis have taken over.