British and American ships are tentatively returning to the Red Sea after Yemen’s Houthi rebels vowed to hold off attacks on vessels linked to both nations, a sign that traffic on one of the world’s main trade routes could normalize after more than a year of disruption.

Shipping companies expressed caution about using the shorter route between Asia and Europe that many ships have avoided for more than a year.

The world’s top three container operators said they fear instability in Gaza and broader regional tensions mean continued danger.

Yemen’s Iran-backed Houthi movement has released the crew of a cargo ship more than a year after its fighters hijacked the vessel in the Red Sea, as part of its campaign of attacks in support of Hamas in its war against Israel.

Yemen’s Houthi rebels have signaled they will limit their attacks in the Red Sea corridor to only Israeli-affiliated ships as a ceasefire in the Gaza Strip takes hold.

Six ships linked to the U.S. and U.K. have successfully transited the area without coming under attack since January 19.

The Houthis announced that they targeted the Harry S. Truman Carrier Strike Group on Friday, casting doubt on whether the Yemen-based terrorist group would stop its attacks on ships in the Red Sea following a ceasefire agreement between Israel and Hamas.

Mandeb strait decreased by 50% after the Yemeni rebels launched maritime attacks, according to the US Energy Information Administration.