"I think it's all complementary," Esper told reporters when asked about the initiative which London, Paris and Berlin have been working on since Tehran seized a British-flagged tanker in the Gulf's strategic Strait of Hormuz last week.

"There will be clearly coordination between us all. CENTCOM will be the coordinating authority," he added, referring to the US Central Command responsible for American forces in the region.

Esper, speaking to reporters for the first time since formally taking office late Tuesday after the US Senate confirmed his appointment, said such an effort would work "whether we do that as one big group, or as subgroups."

The two key things for Washington are to "maintain freedom of navigation" in the Strait of Hormuz and the wider Gulf, and "deterring provocative actions from Iran," the Pentagon chief said.

The United States wants to mount an international coalition to escort ships through the Gulf but so far, few countries have signed on, with Washington's allies concerned about the situation escalating into a full-blown regional conflict.

The Europeans want to safeguard maritime traffic in the Gulf but do not want to align themselves with President Donald Trump's "maximum pressure" strategy in dealing with Iran, as they are hoping to salvage a 2015 international deal with Tehran on its nuclear program.

The United States unilaterally withdrew from that agreement in May last year, and relations between Tehran and Washington have been tense ever since.

US forces are prepared to escort US-flagged ships through the Strait of Hormuz "to the degree that the risk demands it," Esper said.