– Even as planning for a Geneva peace conference on the war in Syria has intensified, the emergence of a group affiliated with Al-Qaida has undermined the chances of negotiating an end to the conflict, a senior State Department official said Monday.

By challenging moderate Syrian rebels, the group, the Islamic State of Iraq and Syria, was forcing them to fight on two fronts and divert resources from their battle with the government of President Bashar Assad, the official said.

By presenting an extremist face to the world, the official said, the group was also aiding Assad's efforts to portray the conflict in Syria as a tug-of-war between the government and jihadists.

"That has to give the regime comfort and confidence, and it will make the task of extracting concessions from the regime at the negotiating table more difficult," said the official, who declined to be identified in keeping with the State Department's protocol for briefing reporters on active diplomacy.

Secretary of State John Kerry, who arrived in Paris on Monday for the first of three days of Middle East diplomacy talks in European capitals, was scheduled to meet with diplomats from 10 nations in London on Tuesday to discuss preparations for a Syria peace conference.

A principal goal of the peace conference, which is expected to be held next month in Geneva although no date has been set, is the establishment of a transitional government "by mutual consent" of Syrians that would not include Assad.

But the senior State Department official said fighters from the Islamic State of Iraq and Syria, known by its initials, ISIS, had hampered the flow of U.S. and other foreign assistance to the moderate resistance inside Syria, diluting the effort to increase the leverage on the Syrian leader.

"It has been very disruptive to our cross border efforts — very disruptive," the official said.

As if to illustrate Assad's determination to ignore the demands of the United States and other nations that he yield power, the Syrian president suggested in an interview with a Beirut television station that he could seek re-election next year. "Personally, I don't see any obstacle to being nominated to run in the next presidential elections," he said in the interview with the television station, Al Mayadeen. Assad said it was too soon to decide but that his choice would be based on "the will of the people."