A US State Department spokesperson told Sputnik Friday "substantial progress" had been made over the last week in the latest round of negotiations as part of the Vienna talks.

The nuclear talks in the Austrian capital are aimed at reviving the nuclear deal, which was abandoned by all parties after the United States withdrew under Trump in 2018 and imposed harsh sanctions on Iran.

"We agree that nothing is agreed until everything is agreed, and also that substantial progress has been made in the last week," the State Department spokesperson said in a statement.

The parties to the Vienna talks - Russia, China, France, the United Kingdom, Germany, and Iran - "can and should agree" on a mutual return to the JCPOA within days if Tehran demonstrates a serious approach, the spokesperson asserted.

On the other hand, Tehran has been blaming Washington for all the delays in the talks. 

"Unless the Europeans agree to Iran's demands and fulfill the nuclear agreement, which stipulates the removal of sanctions and verifying their removal, as well as providing guarantees [to Tehran], we cannot reach a deal," Iranian delegation adviser Seyyed Mohammad Marandi told Al Mayadeen Tuesday.

"Instead of trying to wage a psychological war and providing the media with false information, you can deal with the real issues, and then we can reach a deal sooner or later," he added.

The West still cast the blame on Iran despite the latter proving several times that the issue was not from its end, with the spokesperson saying, "If Iran shows seriousness, we can and should reach an understanding on mutual return to full implementation of the JCPOA within days."

The eighth round of Vienna negotiations on lifting the embargo on Iran resumed between the Iranian delegation and the P4+1 in the Austrian capital on February 10 following an 11-day hiatus for consultations.