TEHRAN, Iran — Iran said yesterday it is likely to resume uranium enrichment-related activities within a week, a process it halted last year to build confidence in talks with European countries and avoid referral to the U.N. Security Council for possible sanctions.

Tehran's announcement came a day after talks in London with European negotiators yielded no results. France, Britain and Germany, acting on behalf of the 25-nation European Union, are seeking guarantees from Iran that it will not use its nuclear program to make weapons, as Washington suspects.

Top Iranian nuclear negotiator Hasan Rowhani was quoted as saying Tehran expects to restart enrichment activities — injecting uranium gas into centrifuges — at its uranium conversion facility in Isfahan.

The central cities of Natanz and Isfahan house the heart of Iran's nuclear program. The Isfahan conversion facility reprocesses uranium-ore concentrate into gas, which is then taken to Natanz and fed into the centrifuges for enrichment.

In Vienna, Austria, a senior diplomat close to the International Atomic Energy Agency said the U.N. nuclear-watchdog body had not been informed of Tehran's intention.