Talks between Iran and six world powers over implementation of a recent nuclear deal will take a break until after Christmas, the Iranian negotiating team said Sunday night, after four days of negotiations.

The announcement came several hours after Iranian Deputy Foreign Minister Abbas Araqchi warned that nuclear negotiations may require a “pause in the talks” due to a conflict of agreement on the technical terms of the deal.

The immediate suspension of the talks was decided upon in a telephone call between Iranian Foreign Minister Mohammad Javad Zarif and EU foreign policy chief Catherine Ashton, Araqchi said.

“During this telephone conversation, it was agreed to continue the negotiations, but with the Christmas holidays in sight it was decided to interrupt and resume [the talks] a week after the holidays,” Araqchi said, according to AFP.

While a new date has not officially been set, Ashton’s spokesperson Maja Kocijancic said they “expect that technical talks will resume before the New Year,” Reuters reported.

The Iranian negotiators met with representatives from the United States, China, Britain, France, Russia and Germany, from Thursday through Sunday in Geneva to discuss the on-the-ground implementation of the guidelines established in the November 24 interim agreement.

However, Araqchi told state television from Geneva on Sunday that the talks have faced trouble. He said there are “incorrect interpretations” in settling a protocol to implement the deal.

“Priorities should be decided to make it clear what actions should be first and what should be done later,” Araqchi said. “But the principle of simultaneous actions by both sides is a main dominant standard in the talks.”

Zarif expressed hope the talks will conclude “sooner or later,” in a joint Tehran press conference with visiting Italian Foreign Minister Emma Bonino. He said the current expert-level talks in Geneva were “slowly” moving forward.

The Iranian delegation met with the six world powers in Vienna on December 12, but cut the meetings short following a decision by the US government to blacklist 19 companies for evading Iranian sanctions. The delegation flew back to Iran a day before negotiations were set to end, stating that the US’s move violated the interim agreement. In spite of this move, the Iranians resumed talks days later in Geneva.

Under the terms of the interim deal agreed in Geneva on November 24, Iran agreed to cap but not freeze  its uranium enrichment in return for the West easing non-core sanctions. The deal has not yet been implemented because “technical details” had to be resolved.

The West fears Iran is pursuing nuclear weapons under its rogue nuclear program. Iran says the program is for peaceful purposes like power generation and medical research.