Tehran, Iran ? Iran will enrich uranium and produce nuclear fuel domestically despite international efforts to curb its atomic program, the nation’s nuclear chief said Saturday, drawing sharp criticism from the United States.

Gholamreza Aghazadeh, head of the Atomic Organization of Iran, also described a European offer to shift Iran’s contentious nuclear enrichment program to Russia as “flawed,” adding that Moscow has not even approached Tehran about the idea.

Meanwhile, state-run television announced that nuclear talks with Europe – aimed at ensuring Iran’s nuclear program cannot produce weapons – will resume Dec. 21 in Vienna, Austria. Talks broke off in August after Tehran restarted uranium conversion, a precursor to enrichment.

Iran is standing its ground amid international pressure to cut back on its nuclear activities, particularly uranium enrichment, which can produce material for use in warheads or fuel for nuclear plants to generate electricity. Iran, one of the world’s largest oil producers, maintains its program is for producing power.

Despite Iranian denials, the United States claims Iran is trying to build atomic weapons and is pushing for Tehran to be hauled before the U.N. Security Council, where it could face economic sanctions for violating a nuclear arms control treaty.