Nuclear talks between Iran and the P5+1 countries will resume on the sidelines of the United Nations General Assembly in New York next month, said the European Union’s foreign policy chief Catherine Ashton on Saturday.

The announcement came amid tensions between Tehran and Washington after the US imposed sanctions on Friday on more than 25 businesses, banks and individuals linked to Iran’s nuclear program.

Iranian President Hassan Rouhani said Saturday that the fresh US sanctions had “further deepened” the mistrust that exists between the long-time foes.

“This is not compatible with the atmosphere of the negotiations,” Rouhani told reporters in Tehran. “It goes against confidence building measures. Mistrust has further deepened.”

Iran and the six world powers reached a six-month interim agreement in February aimed at ending sanctions in exchange for Tehran curbing its nuclear program; a July 20 deadline for reaching a more comprehensive deal was not met and the sides agreed to extend talks until November.

In a post on his unofficial Twitter account, Rouhani said the new measures were “agaisnt the spirit” of the agreement.

Ashton is set to leave her role in October but is expected to keep leading the negotiations with Iran.

“There are ongoing discussions on that (Iran nuclear issue),” Ashton was quoted by Reuters as saying at a news conference. We will use the opportunity of the General Assembly in New York to also do that.”

The UNGA is set for September 16.

Ashton is scheduled to meet Iranian Foreign Minister Mohammed Javad Zarif on Monday, in Brussels.

Western nations have long suspected Iran of covertly seeking a nuclear weapons capability alongside its civilian program, charges denied by Tehran, which insists its program is for entirely peaceful purposes, like power generation and the production of medical isotopes.

Iran and the P5+1 group of world powers — the US, Britain, France, China and Russia plus Germany — hope to reach a comprehensive nuclear agreement by November that would address Western concerns about the nuclear program and lift crippling international sanctions on Tehran.

Rouhani, a reputed moderate, was elected last year after promising to engage the West diplomatically in order to get the sanctions lifted. But he has faced criticism from hardliners who say he has conceded too much in the nuclear talks.