High-level negotiations over Iran’s nuclear program entered their sixth day Thursday after diplomats blew through a June 30 deadline and extended an interim accord by a week.

As the U.N. nuclear agency chief met senior Iranian officials in Tehran, foreign ministers continued discussions in Vienna with few public signs of progress in their attempt to forge a comprehensive deal curbing Iran’s atomic program for relief from crippling sanctions. Work was progressing, albeit slowly, officials said.

“Not at breakthrough moment yet,” British Foreign Secretary Philip Hammond tweeted.

Hammond was the first official Thursday to sit down with U.S. Secretary of State John Kerry, who also planned discussions with the top diplomats of China, France, Germany and the European Union. Kerry was to meet Iranian Foreign Minister Mohammad Javad Zarif in the evening.

Speaking at the Vienna-based Organization for Security and Cooperation in Europe, German Foreign Minister Frank-Walter Steinmeier said all participants had “the serious intention to finalize a deal.” He cited numerous unresolved issues.

“The last steps are the most difficult ones,” Steinmeier told reporters.

Negotiators have given themselves until July 7 to reach agreement.

In Iran’s capital, the International Atomic Energy Agency’s director-general, Yukiya Amano, pressed his agency’s desire to access Iranian nuclear sites to monitor compliance with any accord.

“Iran has a lot invested in this,” Kerry’s deputy, Deputy Secretary of State Tony Blinken, said Thursday. “They need this a lot more than we do.”

“What we don’t know is whether the Iranians have the political space to make a deal,” Blinken said on MSNBC.

(AP)