A U.S. proposal for joint policing mission of the strategic Strait of Hormuz amid rising tensions with Iran is being met with hesitance and skepticism from key allies.

The hesitation appears to reflect a larger rift over the Trump administration’s maximum pressure campaign on Tehran and the U.S. decision to pull out of the 2015 international nuclear deal with Iran last year.

German government spokeswoman Ulrike Demmer said her government is looking for ways to de-escalate tension with Iran, suggesting that American’s monitoring by military force is the opposite of de-escalation.

“For us, it is important to pursue the avenue of diplomacy … and to seek talks with Iran to achieve de-escalation,” she said.

The German news agency dpa reported Wednesday that Foreign Minister Heiko Maas has firmly ruled out German participation in the joint maritime mission for the now.

Newly confirmed Defense Secretary Dr. Mark T. Esper said last week that Operation Sentinel, the proposed coalition from the U.S., is meant to de-escalate tensions after a series of incidents and threats to international tankers had send tensions soaring in recent weeks.

“We’re trying to de-escalate and at the same time message [Iran] very clearly, that without precondition, any time, any place, we’re willing to meet with them to talk about how we get back on into a negotiation,” he said.

U.S. Central Command issued a statement on Operation Sentinel saying it will “enable nations to provide escort to their flagged vessels while taking advantage of the cooperation of participating nations.”

But the “cooperation of participating nations” is slow in coming.

“The German government is reluctant about the concrete U.S. proposal and has therefore not offered contribution, as the overall approach of our policy towards Iran differs significantly from the current U.S. approach,” said Ms. Demmer.

Ms. Demmer said that Germany was interested in a European naval mission that does not include the U.S. and remained “in close coordination with France and Britain.” Berlin, Paris and London all continue to support the 2015 nuclear deal and have tried to find ways around harsh American secondary sanctions on companies doing business with Tehran.

Agence France-Presse reported that France “was not willing to send extra military assets to the Gulf, but would share information and coordinate its currently deployed assets.”

Even the “special relationship” between the United Kingdom and the U.S. is in question.

Former British Foreign Secretary Jeremy Hunt said last week that Britain “will not be part of the U.S. maximum pressure policy on Iran because we remain committed to preserving the Iran nuclear agreement.” The new government of Prime Minister Boris Johnson has yet to signal any change in that stance.

Without joining the U.S. coalition, Britain ordered its Royal Navy to begin escorting its ships in the region after the Iranian seizure of a British-flagged tanker.

But on Tuesday, the U.K. invited representatives from the U.S. and France to a meeting to discuss the Strait of Hormuz situation. British officials said all proposals would be discussed and national governments would have time to review them before taking action.

“Britain hopes it can act as a bridge between the U.S.— which has the largest military presence of a western nation in the region — and countries such as Germany, which is reluctant to get involved in any mission led by Washington,” Dan Sabbagh, a security analyst for the British newspaper The Guardian, wrote.

While the U.S. waits for proposals and coalitions and international partners, Mr. Esper told reporters at the Pentagon that the U.S. “will escort our ships to the degree the threat requires it.”