Washington: Intensifying sectarian and clan violence has presented new opportunities for jihadist groups across the Middle East and raised concerns among US intelligence and counterterrorism officials that militants aligned with Al Qaida could establish a base in Syria capable of threatening Israel and Europe.

The new signs of an energised but fragmented jihadist threat, stretching from Mali and Libya in the west to Yemen in the east, have complicated the narrative of a weakened Al Qaida that President Barack Obama offered in May in a landmark speech heralding the end of the war on terrorism. The leaders of the Senate and House intelligence committees, Senator Dianne Feinstein of California and Representative Mike Rogers of Michigan, raised warnings in an interview on CNN on Sunday when they said that Americans were “not safer” from terrorist attacks than in 2011.

The concerns are based in part on messages relayed this year by Ayman Al Zawahiri, Al Qaida’s overall leader, indicating that he views Syria — where the number of jihadist rebels and foreign fighters is steadily rising — as a promising staging ground.

Some analysts and US officials say the chaos there could force the Obama administration to take a more active role to stave off potential threats among the opposition groups fighting against the government of President Bashar Al Assad. But striking at jihadist groups in Syria would pose formidable political, military and legal obstacles, and could come at the cost of some kind of accommodation — even if only temporary or tactical — with Al Assad’s brutal but secular government, analysts say.

“We need to start talking to the Al Assad regime again” about counterterrorism and other issues of shared concern, said Ryan C. Crocker, a veteran diplomat who has served in Syria, Iraq and Afghanistan. “It will have to be done very, very quietly. But bad as Al Assad is, he is not as bad as the jihadis who would take over in his absence.”

It is not clear whether or when the White House would be willing to make such an abrupt shift in approach after years of supporting the Syrian opposition and calling for Al Assad’s ouster. It would certainly require delicate negotiations with Middle Eastern allies who were early and eager supporters of Syrian rebel groups, notably Saudi Arabia.

One growing source of concern is the number of Muslims from Western countries who have gone to fight in Syria and might eventually return home and pose a terrorist threat. Analysts say at least 1,200 European Muslims have gone to Syria since the start of the war to join the fight, and dozens of Americans.

Across the region, a rising tide of Islamist militancy — fuelled partly by sectarian violence and partly by the collapse of Egypt’s Muslim Brotherhood in the face of opposition from the country’s military — has contributed to a recent wave of attacks, including bombings in Lebanon and the Sinai Peninsula as well as the daily carnage in Syria and Iraq.

The violence has underscored the continuing disarray across the Middle East in the wake of the 2011 Arab Spring uprisings. Above all, it is the chaos of Syria, where foreign jihadis appear to be building to a critical mass and have overwhelmed the Western strategy of support for the moderate opposition, that could drive the Obama administration toward greater involvement, analysts say.

But it is not at all clear what form that involvement might take. The use of drones is one option, but not the only one. In early October, US commandos carried out raids in Libya and Somalia aimed at capturing terrorism suspects. One of those raids was successful, the other not.

To some extent, infighting among the jihadist groups in Syria has recently mitigated the threat there, but it is not clear how long that will last. Zawahiri sent an envoy, Abu Khalid Al Suri, in an effort to resolve disputes between the two main factions, the Nusra Front and the Islamic State of Iraq and Syria.