Iran rejected a proposal to curb uranium enrichment during the second day of nuclear talks with Western powers in Baghdad Thursday.

The six-nation negotiating bloc, made up of the five permanent members of the U.N. Security Council -- Britain, China, France, Russia and the U.S. -- plus Germany, demanded that Iran scale back uranium production by 20 percent.

In exchange, they offered Iran medical isotopes, nuclear safety assistance and civilian aviation components, but did not offer to lift economic sanctions imposed by the U.S. and European powers targeting Iran's oil exports, which are crucial for raising revenue to fund its nuclear program.

Iran rejected the proposal, demanding a lifting of the sanctions in exchange for granting access to U.N. inspectors to its nuclear facilities.

Israel has threatened a pre-emptive strike on Iran's nuclear facilities if uranium enrichment is not halted and has criticized Iran's approach at the talks as a ploy for time.

The U.S., Israel and other Western allies believe that Iran's uranium enrichment is intended for the production of nuclear weapons, though China and Russia have opposed this claim and prevented U.N. sanctions against Iran within the Security Council.

Talks in Baghdad are expected to conclude Thursday, but another round has been proposed next month in Geneva, which Iran has expressed opposition to.