The British Foreign Office has confirmed that foreign ministers from all six nations will attend, including Britain, China, France,
Germany, Russia and the United States.
The discussions -- due to take place in Lancaster House in central London – might also extend into dinner.
US Secretary of State Condoleezza Rice will attend the meeting following her whistle-stop tour of the Middle East.
Sanctions loom
The latest talks come as the United Nations Security Council prepares to discuss diplomatic or economic sanctions against Iran, following failed efforts to convince Tehran to freeze the development of nuclear fuel.
"I expect the Iranian dossier to re-emerge in New York in the course of next week," Britain's ambassador to the United Nations, Emyr Jones Parry, said in New York.
The West suspects Iran may be seeking to develop a nuclear weapon, but its government insists its nuclear program is solely for energy production and has refused to suspend the enrichment of uranium.
The six powers – including the permanent five, veto-wielding members of the Security Council plus Germany -- agreed to set a new deadline this week for Iran to comply with a UN resolution demanding it freeze uranium enrichment.