WASHINGTON - US Secretary of State John Kerry headed for Europe Monday for talks on Iran's nuclear programs, a week before the deadline for a comprehensive deal expires.

"We are obviously entering in a key period with the negotiations regarding Iran's nuclear program," Kerry said at a forum in Washington earlier in the Monday, before traveling to London for meetings with officials from Europe and the Middle East.

Negotiators from Iran and world powers will meet Tuesday in the Austrian capital of Vienna for a new round of talks, which will probably continue until the Nov 24 deadline, according to an Iranian negotiator.

Kerry will also travel to Vienna this week, but the time of his arrival is undecided, Jeff Rathke, director of US State Department Press Office, said at a press briefing Monday.

Iran and the P5+1 group -- the US, Britain, France, China, Russia and Germany -- reached an interim deal last November to halt Tehran's nuclear programs in exchange of limited easing of sanctions.

After failing to narrow down gaps on core issues during six- month negotiations for a comprehensive deal, Iran and the P5+1 group agreed in July to extend the nuclear talks for another four months till Nov 24.

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