Deputy Foreign Minister Abbas Araghchi will meet Catherine Ashton on Tuesday, as part of a Brussels visit meant to focus on "implementing the joint action plan," said Michael Mann, Ashton's spokesman.
The two sides last month hashed out an initial deal that foresees Iran curbing some nuclear activities for six months, in exchange for an easing of international sanctions.
But the US then proceeded with additional sanctions against Tehran, expanding its blacklist of individuals and companies.
Iran accused the US of acting against the spirit of the current talks and withdrew delegates from a meeting in Vienna over technical details of the agreement.
Ashton said Monday she expected the technical talks with the Iranians to soon resume.
"We sorted out most of the detail, but inevitably there are one or two areas where we need to think very carefully about how the implementation is going to work," she noted. "The Iranians are in touch with us. I'm expecting them to start work again very soon."
She was speaking ahead of a meeting of EU foreign ministers, who endorsed the action plan agreed to with Iran and pledged to suspend some of the EU's sanctions "immediately after" it is verified that Tehran has implemented its "nuclear-related measures."
"Iran has to implement its commitments in good faith," they said, noting the agreement should "build trust and reduce tensions."
"There remain difficult negotiations to be had over the coming months," British Foreign Secretary William Hague said. "In the meantime, we have to maintain our vigilance on sanctions, ... so that Iran has a clear incentive to make a comprehensive deal."
"The first step was encouraging, but there's still a long way to go," Dutch Foreign Minister Frans Timmermans agreed. "I believe the EU should be very careful in combining the next step Iran needs to take with the lifting of sanctions - but not earlier."
Iranian Foreign Minister Mohammad Javad Zarif called the recent US sanctions against a few Iranian entities a very wrong move, but says Tehran still honors the interim nuclear deal it reached with the Sextet over Iran's nuclear energy program.
He said the US move was a very wrong move.
The US Departments of Treasury and State on December 12 issued new sanctions against a number of companies and individuals for “providing support for” Iran’s nuclear program.
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