China urged Iran on Tuesday to respond to a package of incentives to stop enriching uranium and called on G8 powers to show patience, saying the standoff over Iran's nuclear plans had entered a crucial phase.

Iran's nuclear ambitions are expected to dominate the Group of Eight summit in Moscow this week as members wait for Tehran to formally respond to a proposal backed by the five permanent members of the U.N Security Council and Germany.

Those powers have offered Iran diplomatic and economic incentives in return for halting uranium enrichment -- a step Iran has repeatedly scorned as violating its right to civilian nuclear power.

Washington and other Western capitals say Iran wants to make nuclear weapons.

"The Iran nuclear issue is at a crucial phase," Chinese Foreign Ministry spokeswoman Jiang Yu told a news conference in Beijing.

"We hope that Iran will pay attention to the concerns of the international community and respond as soon as possible to the basket of proposals.

"We also hope that the other sides will exercise patience and restraint and seriously consider Iran's reasonable concerns."

The G8 nations -- the United States, Russia, Canada, France, Germany, Italy, Japan and Britain -- have told Iran they expect a response to the offer by July 5, and U.N. Security Council action could loom if Tehran does not have an answer by July 12.

Iran has said it will answer by August 22.