US agencies and the European Union will begin the process of suspending their nuclear-related sanctions after Iran fulfills its promise.

As time ran out for US lawmakers to halt the Iran nuclear deal on Thursday, officials in Washington turned their attention to ensuring that Tehran lives up to its side of the bargain.

Senior administration officials said the "ball is in Iran's court" as Iran seeks to convince the international community its nuclear program, which it insists is strictly civilian, has been limited short of the threshold for the capability of producing an atomic weapon.

US President Barack Obama and Secretary of State John Kerry marked the change in focus by naming a senior diplomat, Stephen Mull, as coordinator of the US effort to verify the implementation of the deal.

And, as the 60-day period which Congress had to study the deal expired without skeptical lawmakers having been able to derail it, Obama dropped in to the State Department to congratulate the team.

"It is vitally important that we now have the right team with the right leader in place to ensure the successful implementation of the Joint Comprehensive Plan of Action," Kerry said, announcing Mull's appointment.

Mull's team will be based at the State Department and include experts from several US economic, scientific, enforcement and intelligence agencies.

"There's a lot that Iran needs to do before it can get the sanctions relief that we're offering in the deal," a senior US official said, citing a timeframe of "several months" before the agreement can be enacted.

"Iran needs to make major changes to its core nuclear infrastructure," he said, starting on so-called adoption day - 18 October - and continuing to "implementation day" somewhere down the line.

Earlier on Thursday, Senate Democrats defeated a Republican attempt to tie a vote on the nuclear deal with a stipulation that Iran recognize the so-called 'Israel' and release American prisoners before sanctions are lifted.

During the implementation period, the IAEA will work with Iran to install technical monitoring systems and begin inspections.

After this point is reached, foreign countries and companies that had been barred by the US and some other international nuclear-related sanctions from dealing with Iran will be free to resume trade.

One senior administration official said the US would begin issuing waivers for companies wanting to deal with Iran on adoption day, 18 October.

Meanwhile, US agencies and the European Union will begin the process of suspending their nuclear-related sanctions after Iran has been seen to have fulfilled its promise.