MANAMA (Reuters) - Qatar and Kuwait have told the United States that they will join a U.S.-led naval coalition in the Gulf which was established in response to a series of attacks on oil tankers, a U.S. military official said on Monday.

The coalition, based out of Bahrain and known as the International Maritime Security Construct (IMSC), was formed after a series of attacks earlier this year heightened the risk of disruption to Gulf oil exports shipped through the Strait of Hormuz.

The United States blamed the attacks on Iran, which Tehran denied.

“Qatar and Kuwait have already told us they are going to join, so it is just a matter of time,” said U.S. Army Colonel John Conklin, chief of staff of the coalition.

Conklin said they were expected to provide personnel and patrol boats. The United States was in talks with Canada about joining the initiative, said Conklin, who spoke during a trip to the Middle East by Chairman of the Joint Chiefs of Staff General Mark Milley. Milley arrived in Saudi Arabia on Monday.

So far the coalition has received a lukewarm response with Albania, Australia, Bahrain, Saudi Arabia, the United Arab Emirates and the United Kingdom joining.

At the same time, France is spearheading a European-led mission independent of the U.S-led maritime initiative, which some European countries feared would make U.S.-Iranian tensions worse.

“To my knowledge, nobody has joined (the French) coalition yet and they’ve been trying for a while but they haven’t been very successful,” Conklin said.

Last week Yemen’s Iran-aligned Houthi movement released three vessels and 16 people it had seized at sea around Yemen. Of the vessels freed on Tuesday, one was Saudi Arabia-flagged.

Conklin said the coalition had seen the incident but the Saudi ship had actually entered Yemeni waters and based on international law there was not much that could be done.

Houthi forces have been driven away from most of Yemen’s coast during the conflict, but still hold Hodeidah, the country’s biggest Red Sea port and the base of the group’s navy.