VIENNA (AP) — With a deadline approaching for a nuclear deal, an Iranian official said Sunday that the discussion may soon have to shift from trying to reach an agreement to extending negotiations past the target date.

The official, a member of the Iranian delegation in Vienna, said the tipping point could come Sunday night, with Iran and six world powers deciding that their differences are too big to meet the Monday deadline, and switching to extension mode.

From that point on, he said, the negotiations would focus on reaching a "general political agreement" on what both sides are committed to resolving. The official, who demanded anonymity as a condition for briefing the media, said that talks would then be held in the near future to sign that agreement, leading to more negotiations on outstanding issues.

Should such a plan be agreed upon, one possibility for a resumption of talks would be the first week in December when U.S. Secretary of State Kerry plans to return to Europe for a previously scheduled NATO foreign ministers meeting in Brussels, and an international conference in London.

Meanwhile, foreign ministers for most of the seven nations taking part in the Austria talks are adding their political muscle to try and advance the negotiations.

Since landing in Vienna on Thursday, Kerry has met repeatedly with Iranian Foreign Minister Mohammad Javad Zarif and other key officials.

German Foreign Minister Frank-Walter Steinmeier arrived Saturday, while Russian Foreign Minister Sergey Lavrov and his French, German and British counterparts are scheduled to join in later Sunday.

But diplomats familiar with the negotiations said that since Friday night sizable gaps have remained between the U.S. and Iran on the key issue of how deeply Tehran would have to reduce nuclear activities that could be turned to making arms.

Iran denies any interest in such weapons but is negotiating because it wants an end to nuclear-related sanctions.

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Margaret Childs contributed from Vienna.