DUBAI: "Bitter experience" with broken US promises has made it inevitable that Iran will push to defend its interests by securing a "reliable" nuclear agreement, its top security official said on Wednesday, according to the Nour-news website.

"Bitter experience with the US breach of promises and European inaction have made it inevitable to meet the requirements for a reliable, balanced and sustainable agreement," Ali Shamkhani was quoted as saying at a meeting between Iranian parliamentarians and the Supreme National Security Council.

All parties involved in the talks say progress has been made toward the restoration of the pact to curb Tehran's nuclear programme in exchange for sanctions relief, which the United States abandoned in 2018. But both Tehran and Washington have said there are still some significant differences to overcome.

Despite progress in the negotiations, the key sticking point is that Tehran wants the issue of uranium traces found at several old but undeclared sites in Iran to be dropped and closed forever, an Iranian official told Reuters.