Secretary of State John Kerry says the United States, its negotiating partners and Iran are making progress during talks over Tehran’s nuclear program.

"We are working very, very hard and we have some very difficult issues but we believe we're making progress and we're going to continue to work because of that," Kerry said on Wednesday.

The top US diplomat made the comments during a break from the nuclear negotiations in the Austrian capital city of Vienna.

Representatives from Iran and the P5+1 group of countries – the US, Russia, China, Britain, France, and Germany – are working together in Vienna to finalize a nuclear deal.

The two sides extended their self-imposed end-of-June deadline one more week. The deadline is extended to July 7.

Iranian Foreign Minister Mohammad Javad Zarif also said the talks are making progress.

"We have made progress and we will make progress and we will use every opportunity to make progress," Zarif said.

By Press TV