The United States on September 24 will host a summit of UN Security Council member states on nuclear non-proliferation, the White House confirmed on Thursday.

President Barack Obama is to chair the meeting, which will be held alongside the UN General Assembly at UN headquarters in New York.

It will be the first time a US president leads such a summit and just the fifth in UN history that such a summit is being held, White House spokesman Robert Gibbs told reporters.

"We did ask for it, and are heading it," Gibbs said.

The summit was first announced by the US ambassador to the United Nations Susan Rice last month.

Rice said at the time that the session would "be focused on nuclear nonproliferation and nuclear disarmament broadly and not on any specific countries."

She said Obama would preside over the special meeting a day after he is due to address the UN General Assembly session.

The White House confirmation of the meeting came as the State Department said that a package of proposals submitted by Iran to the United States, China, Russia, Britain, France and Germany was "not really responsive" to concerns about its disputed nuclear program.

The White House on Wednesday said Iran must show progress towards ending its "illicit" nuclear activities, as Tehran delivered new proposals on how to resolve a standoff over its atomic program.

Washington fears Tehran's nuclear program will be used to build an atom bomb. Iran denies the charge, saying it is aimed at generating electricity.

In May, the five veto-wielding permanent members of the Security Council -- Britain, China, France, Russia and the United States -- reaffirmed their support for the Nuclear Non-Proliferation Treaty (NPT) and hailed progress made in preparatory talks for the next NPT review conference in 2010.

They also urged all NPT signatories to help ensure "a successful and balanced review" next year.

The last NPT review conference, which gathers NPT signatory states and seeks to rescue the treaty from charges it has become obsolete, ended in disarray in May 2005 with no agreement from the participating countries.

The conferences have been held every five years since the NPT was ratified in 1970. There are currently 189 signatory countries to the treaty.