WASHINGTON (AFP) - New United States Secretary of State John Kerry on Friday said the window of diplomacy remains open for Iran as it prepares to meet later this month with world powers for new talks on its nuclear programme.

"The choice is really ultimately up to Iran," Mr Kerry told his first press conference since becoming America's top diplomat this week.

"The international community is ready to respond if Iran comes prepared to talk real substance and to address the concerns, which could not be more clear, about their nuclear programme.

"If they don't, then they will choose to leave themselves more isolated.

That's the choice," Mr Kerry said, speaking after his first bilateral talks with Canadian Foreign Minister John Baird.

Tehran has agreed to meet with the six world powers working to rein its suspect nuclear programme for a new round of talks in Almaty, Kazakhstan on Feb 26.

They last met in May in Baghdad, when the so-called P5+1 - the US, China, Russia, Britain, France and Germany - demanded Iran scale back its uranium enrichment, the most worrying part of its programme.

But because the P5+1 stopped short of offering relief from the sanctions, Iran walked away at the next round of talks in Russia.

British Foreign Secretary William Hague has said the P5+1 will put forward an "updated and credible" offer to Iranian leaders at the Almaty talks.

Iran insists its nuclear programme is peaceful, but many in the international community suspect that Tehran's real aim is to develop an atomic bomb.