US Undersecretary of State Nicholas Burns pressed for harsher UN sanctions against Iran for its nuclear program on Friday, while Iran’s former president said talks with the UN atomic watchdog were progressing and warned against threatening his country.

After talks on Thursday in Vienna with Mohamed ElBaradei, head of the UN’s International Atomic Energy Agency, Burns told reporters on Friday that Washington wants a resolution on a third round of UN Security Council sanctions passed soon.

“There are sanctions being implemented and there will be a third Security Council sanctions resolution,” if Iran continues to defy the council, Burns said.

But Iran’s former president, Hashemi Rafsanjani, said on Friday that talks between Iran and the UN nuclear watchdog were making progress and he warned the US to avoid resorting to threats.