VIENNA, Sept. 1 (AFP) - The signatories to the faltering Iran nuclear deal meet in Vienna on Tuesday (Sep 1) as the US is urging international sanctions on the Islamic republic to be reimposed and an arms embargo to be extended.

Britain, France, Germany, China and Russia are struggling to save the 2015 landmark accord with Iran, which has been progressively stepping up its nuclear activities since last year.

Tehran insists it is entitled to do so under the deal - which swapped sanctions relief for Iran's agreement to scale back its nuclear programme - following the US withdrawal from the accord in 2018 and the reimposition of sanctions.

In a boost to Tuesday's talks, the Iranian atomic energy last week agreed for inspectors of the UN nuclear watchdog to visit two sites suspected of having hosted undeclared activity in the early 2000s.

The International Atomic Energy Agency (IAEA) head Rafael Grossi had travelled to Iran on his first trip since taking up the top post last year and after months of calling for access.

Results from any site visits are, however, expected to take three months, according to a diplomat familiar with the matter, so "it risks being a problem then with the Iranians" if anything undeclared and nuclear-related is found.