The U.S. carried out new airstrikes on Yemen, expanding the biggest U.S. military operation in the Middle East since President Trump took office.

The airstrikes come a few days after the Houthis said they would resume attacks on Israeli vessels sailing in waters off Yemen in response to Israel’s blockade on Gaza.

The strikes represent the biggest U.S. military operation in the Middle East since Trump took office, and come as the U.S. increases sanctions pressure on Iran while trying to bring it to the negotiating table over its nuclear program.