China on Tuesday called for increased diplomatic efforts and an early agreement for an internationally-backed nuclear fuel proposal for Tehran after Iran started its higher-grade uranium enrichment program.

Iran informed the International Atomic Energy Agency (IAEA) about its plan to start its enrichment activities to the purity of 20 percent on Tuesday, provoking fresh warnings by Western countries of new sanctions.

"We note the related reports. We expect and back all sides to reach an early agreement on the IAEA-raised draft proposal regarding the Tehran research reactor, which will help solve the issue," Foreign Ministry spokesman Ma Zhaoxu told a regular briefing on Tuesday.

Under the IAEA-brokered deal, Iran would be supplied with nuclear fuel for the medical research reactor in Tehran in exchange for its low-enriched uranium.

Reviewing the recent consultations of the six countries, including the United States, Russia, China, France, Britain and Germany, on Iran nuclear issue, Ma said, "China hopes all relevant parties will step up diplomatic efforts and make progress in dialogue and negotiations."