Iran’s dispatch of a warship to the Red Sea is its most audacious move yet to challenge U.S. forces in the key trade route, emboldening Houthi militants whose missiles have disrupted shipping over the past two months.

Tehran is unlikely to want direct confrontation — its old frigate being no match for the U.S.-led maritime task force patrolling the waters off Yemen — but it takes the projection of Iranian power in the region to another level. That is raising tensions after the Houthis started attacking vessels they claimed were headed to or owned by firms in Israel in a bid to end the military assault on the Gaza Strip.

Iran has rejected calls from Western powers to pressure the Houthis to end their attacks in the Red Sea. Some of the latest ships targeted by the rebels don’t have clear links to Israel, according to Kevjn Lim, a Tel Aviv-based analyst at S&P Global Market Intelligence. That includes an attack on an AP Moller-Maersk A/S container ship, after Denmark said it was joining the task force.