The UN and Russia said the move was encouraging, but the US expressed concern at Iran's statement that it would continue to enrich uranium.

The US and the UK said work on a UN resolution imposing more sanctions on Iran would continue.

The West suspects Iran's nuclear programme is aimed at making weapons.

Iran insists it is solely designed to meet its energy needs.

Iran hopes the new agreement - in which it would ship 1,200kg (2,645lb) of low-enriched uranium to Turkey in return for higher-grade nuclear fuel for a research reactor - would avert new sanctions.