Previous round of talks in Geneva
Previous round of talks in Geneva Reuters

Talks between Iran and world powers on implementing last month's nuclear deal will resume Thursday in Geneva, a spokesman for EU foreign policy chief Catherine Ashton told AFP on Wednesday.

"The technical talks will be resumed tomorrow and continue until Friday" in Geneva, said the spokesman, Michael Mann.

The experts held four days of talks in Vienna last week but the Iranians walked out after Washington expanded its sanctions blacklist against Tehran.

Iran's state broadcaster quoted deputy foreign minister Abbas Araqchi as confirming the talks will resume and adding that the two days of talks could be extended to the weekend.

According to AFP, Araqchi said Tehran was prepared to continue the talks after Ashton "made the assurance that the world powers, particularly the United States, will continue the talks in goodwill and that they are serious about implementing the deal."

Under the November 24 accord struck in Geneva, Iran agreed to roll back parts of its nuclear program for six months in exchange for modest sanctions relief and a promise not to impose new sanctions.

But the United States last week put a dozen overseas companies on a blacklist for evading its sanctions, angering Tehran even though Washington said the new measures did not constitute new sanctions.

On Tuesday, Araqchi said the U.S. move remains of "serious concern, it's against the spirit of the deal."

"We agreed to move on the basis of good will and good faith. And to add these new companies to the list of sanctions, it's not goodwill," he said.

On Sunday, Iran’s Foreign Minister, Mohammad Javad Zarif, said his country will keep talking with world powers on its disputed nuclear program despite the U.S. blacklist.

Zarif expressed Iran's "discontent" in a phone call with Secretary of State John Kerry, the Iranian news agency Fars reported on Monday. The State Department confirmed the call took place.

Diplomats told AFP that the talks last week in Vienna were heavy-going as the parties sought to work out a carefully calibrated process of when sanctions would be eased, when the nuclear freeze would start and how it would be verified.

They insisted, however, that the discussions were not any harder than expected and that the differences would eventually be ironed out.

The blacklisting of the companies last Thursday came as two top senators bowed to White House pleas not to introduce new sanctions and House lawmakers admitted that a new Iran sanctions measure currently under consideration by the Senate is “all but dead in the water.”

The fact that senators are holding off on the sanctions is a victory for the Obama administration, which has waged an aggressive campaign to convince lawmakers to postpone passing new sanctions on Iran.