The Arab Gulf states have not asked the U.S. to declare war on Iran, but many are now urging Washington not to stop halfway, leaving the Islamic Republic free to continue threatening the Gulf’s vital oil supply routes and the economies that depend on them, three Gulf sources told Reuters.

At the same time, these sources, along with five Western and Arab diplomats, say that Washington is pressing Gulf states to participate in the U.S. and Israel’s war. According to three of them, Donald Trump wants to demonstrate regional support for the campaign to boost both its international legitimacy and domestic backing.

“There is a broad sense across the Gulf that Iran has crossed every red line with every Gulf country,” said Abdulaziz Al-Sager, chairman of the Gulf Research Center based in Saudi Arabia.

“At first, we defended them and opposed war,” he said. “But once they began directing attacks against us, they became enemies. There is no other way to describe them.”

The attacks have heightened Gulf fears that leaving Iran with any significant offensive weaponry or weapons-making capability could encourage it to hold the region’s vital energy lifeline “hostage” whenever tensions rise.

As the war enters its third week, with U.S. and Israeli airstrikes intensifying and Iran firing on American bases and political targets across the Gulf, a Gulf source says the prevailing sentiment among leaders is clear: Trump must weaken Iran’s military capability comprehensively.

The alternative, the source says, is living under constant threat. If Iran is not seriously weakened, it will continue to hold the region “hostage.”