TEHRAN-- British officials visited Iran last week to discuss ways of paying the United Kingdom’s decades-old debt to Iran, which Tehran’s envoy to London said is held up by U.S. sanctions.

Iranian Ambassador to the UK Mohsen Baharvand told reporters in London on Friday that Iran had nearly reached an agreement on the debt with the British government this summer.

"We had a deal. We signed it. But two days after the signature of that deal, the UK government said they could not implement it because of U.S. sanctions,” The Guardian quoted Baharvand as saying.

Baharvand said he is hopeful for an agreement and that the “obstacles are not insurmountable.”

“We are trying. We should not be that pessimistic. We are working with our Foreign Office colleagues maybe to reach that deal. We are in the process of discussions," he said.

Baharvand said the British delegation to Tehran last week discussed the release of imprisoned British nationals, including Nazanin Zaghari-Ratcliffe, a British-Iranian citizen who was arrested in 2016.