Tehran has already portrayed the deal as a victory

Top US diplomat Marco Rubio was in Bahrain on Thursday after promising Gulf allies that Washington would protect their interests as it seeks to hammer out a final settlement to end the war with Iran.

With diplomacy in full swing, Brent crude fell to its lowest price since the start of the war in February, which has crippled global oil supplies flowing from the crude-rich Middle East.

President Donald Trump met with NATO chief Mark Rutte at the White House on Wednesday and said the United States was “doing great” in negotiations with Iran.

Trump also asked Congress for nearly $88 billion in supplemental funding, mostly to cover the spiralling cost of the war, just a day after Congress called on him to end the conflict unless lawmakers explicitly authorise military action.