The leaders of Germany, France, the United Kingdom and the United States on Saturday expressed their “grave and growing concern” about Iran’s nuclear program after a meeting on the sidelines of the Group of 20 summit in Rome.

German Chancellor Angela Merkel, French President Emmanuel Macron, British Prime Minister Boris Johnson and US President Joe Biden said in a statement quoted by Euronews that Iran “has accelerated the pace of provocative nuclear steps, such as the production of highly enriched uranium and enriched uranium metal.”

“Iran has no credible civilian need for either measure, but both are important to nuclear weapons programs,” they added.

The four leaders said the situation underscored the importance of Iran and the United States coming back to the 2015 nuclear deal known as the Joint Comprehensive Plan of Action.

Iran has gradually scaled back its compliance with the 2015 nuclear deal it signed with world powers in response to former US President Donald Trump’s withdrawal from the agreement in May of 2018.

The previous Iranian government, headed by former President Hassan Rouhani, had been holding indirect talks with the Biden administration on a return to the agreement.

However, the negotiations were adjourned on June 20, two days after Ebrahim Raisi won Iran’s presidential election, and no date has been set for a resumption of dialogue.

This past week, Ali Bagheri Kani, Iran’s new chief negotiator on the nuclear issue, announced on Twitter that negotiations with western powers in Vienna over the Islamic Republic’s nuclear program would resume by the end of November.

In response, a State Department spokesperson urged Iran to show “good faith” in the talks.

“As we have also been clear, this window will not remain open forever as Iran continues to take provocative nuclear steps, so we hope that they come to Vienna to negotiate quickly and in good faith,” said the spokesperson.

Macron, Johnson, Merkel and Biden said in Saturday’s statement they believed it was “remains possible to quickly reach and implement an understanding on return to full compliance to ensure for the long term that Iran’s nuclear program is exclusively for peaceful purposes, and to provide sanctions lifting with long lasting implications for Iran’s economic growth.”

They called on Raisi to avoid a “dangerous escalation” of the situation.