A senior U.S. intelligence official on Tuesday warned of a "very real" risk of extremist groups gaining control of Syrian chemical or biological weapons.

"The current instability in Syria presents a perfect opportunity for al-Qaida and associated groups to acquire these weapons [of mass destruction] or their components," U.S. Defense Intelligence Agency Director Lt. Gen. Michael Flynn said in Tuesday testimony before the Senate Armed Services Committee, citing the terrorist organizations' longtime stated interest in acquiring the most dangerous arms.

His remarks stand in contrast to some recent comments by U.S. diplomats who have played down the risk that extremists might seize Syrian chemical arms as they are transported to a coastal city for international removal and destruction.

Syrian President Bashar Assad's government has blamed delays in moving these sensitive warfare materials out of the country on security concerns, amid assertions that the sensitive convoys already have come under rebel attack. Damascus last year agreed to U.S. and Russian demands that it surrender its entire chemical arsenal following a major sarin gas attack that allegedly killed more than 1,400 civilians.

"While Syria's stockpiles are currently under the control of the regime, the movement of these weapons from their current locations for disposal or other reasons drastically increases the risk of these weapons or their components falling into the wrong hands," Flynn said. "There is also the very real possibility that extremists in the Syrian opposition could overrun and exploit chemical and biological weapons storage facilities before all of these materials are removed."

Damascus this week said nearly all of most of its most deadly chemicals would be moved out of Syria by the end of the month -- two months past a deadline set by international authorities.

At the Tuesday hearing, U.S. National Intelligence Director James Clapper told the panel it was "hard to discern" whether the Syrian delays were due to legitimate security concerns. Instead, he indicated, the lag times could reflect a scheme by Damascus aimed at lengthening the chemical disarmament process for "as long as possible because it ... serves to implicitly legitimize Assad."

U.S. Ambassador to the United Nations Samantha Power in comments to reporters last week seemed to minimize Damascus' argument that extremist threats to chemicals under transport justified the delays.

"We know the regime has the ability to move these weapons and materials because they have moved them multiple times over the course of this conflict," Power said. "It is time for the Assad government to stop its foot-dragging."

On Tuesday, Clapper also told the Senate panel there are projected to be in excess of 7,500 foreign fighters hailing from about 50 countries currently in Syria. "Among them are a small group of [Afghanistan-Pakistan] al-Qaida veterans who have aspirations for external attacks in Europe, if not the [U.S.] homeland itself," he said.