Secretary of State Marco Rubio promised Gulf allies of the United States on Wednesday that Washington would protect their interests as it seeks to hammer out a final settlement of the Middle East war in talks with Iran. President Donald Trump met with NATO chief Mark Rutte at the White House, meanwhile, and said the United States was "doing great" in negotiations with Iran. Trump also asked Congress on Wednesday for nearly $88 billion in supplemental funding, most of it for the Pentagon to cover the cost of the Iran war. The proposal landed a day after Congress passed a largely symbolic resolution calling on Trump to end US hostilities with Iran unless lawmakers explicitly authorise military action. Read moreUS military says senior Islamic State group leader killed in Syria air strike Rubio is on a regional tour to reassure the Gulf states, which were targeted by Tehran's missiles and drones during the conflict and saw their crucial oil and gas shipments effectively cut off by an Iranian blockade of the Strait of Hormuz. Tehran has emerged emboldened from the war, vowing not to relinquish control of the vital waterway and going so far as to call its initial deal with Washington to stop the fighting "a declaration of America's defeat." During a visit to Kuwait City, Rubio said Washington would be on the same page as Gulf states as it wrangles with Iran over a permanent settlement to the conflict. "We're going to be completely aligned with our partners in the Gulf," he said, adding that the United States would "engage them on conversations about every decision that's made with regards to this negotiation." Rubio is due to attend a Gulf Cooperation Council meeting in Bahrain on Thursday after sitting down with the leaders of Kuwait and the United Arab Emirates on Wednesday. The initial US-Iran deal, which sets out a 60-day negotiating process aimed at reaching a long-term agreement, failed to address Gulf nations' long-standing concerns about Iran's missile program and regional proxies. But Rubio insisted Washington was "not going to do anything that undermines the security of our allies."