Hello and welcome to the Guardian’s continuing coverage of the crisis in the Middle East.

US secretary of state Marco Rubio said on Monday that a deal to end the war with Iran could materialise “today”.

His comments came after oil prices plunged and Asian shares rose earlier in the day amid optimism that the US and Iran were close to an agreement that might secure a lasting end to the three-month war and reopen the strait of Hormuz. Oil prices hit a two-week low, with Brent crude futures falling 4.5% to $98.83 a barrel by 11.50pm GMT.

“We thought we might have some news last night, maybe today – I wouldn’t read too much into it,” Rubio said in New Delhi of a potential agreement.

“We have what I think is a pretty solid thing on the table in terms of their ability to open up the straits,” he said. “It has a lot of support in the Gulf.”

Rubio’s remarks came after Donald Trump tempered expectations of a deal, saying on Sunday that he had told his negotiators “not to rush”. Negotiations with Iran were “proceeding in an orderly and constructive manner”, the US president said.

Middle East officials told the Associated Press on Sunday that the US was close to reaching a deal with Iran that would end the war and reopen the strait, a vital conduit for global energy supplies.

On Sunday Trump said the US blockade on Iranian ships in the Hormuz strait would “remain in full force and effect until an agreement is reached, certified and signed”. “Both sides must take their time and get it right,” he added.

As details of the possible agreement emerged over the weekend, critics including Trump’s former secretary of state Mike Pompeo said it offered little beyond the 2015 Iran nuclear deal negotiated by former president Barack Obama, from which Trump withdrew during his first term.

Chris Van Hollen, a Democratic member of the Senate foreign relations committee, said the deal’s reported outlines would amount to little more than “the prewar status quo” with Iran.