As part of his push to revisit the 2015 nuclear deal later this week, US President Donald Trump is expected to unveil a broader plan to roll back Iranian influence across the Middle East.

Former US diplomats posted to the region, however, are deeply skeptical that the United States can come out ahead in a geopolitical confrontation with Tehran. While the White House has expressed frustration with the gains made by Iran-backed Shiite groups in places such as Iraq, Syria and Yemen, three US ambassadors warned that changing the situation on the ground would be costly and difficult to achieve.

“I see no good options vis-a-vis Iran in Iraq or Syria,” former US Ambassador to Iraq and Syria Ryan Crocker told Al-Monitor. “They’re not going to be easily persuaded, and I don’t think we have the wherewithal to push them out.”

Trump has made no secret of his disdain for the nuclear deal negotiated by his predecessor, which he argues has constrained America’s ability to confront Tehran on a range of other issues such as its ballistic missile program and support for proxy forces. He is widely expected to refuse to certify that the deal is in America’s national security interest ahead of an Oct. 15 deadline and to ask Congress to consider more sanctions while stopping short of pulling out of the Joint Comprehensive Plan of Action (JCPOA).