The Washington Post’s Liz Sly and David Ignatius look back at the bloody Syrian civil war--thousands killed, a country in ruins and borders breached by a tide of refugees. What will the future hold for the Syrian people and the al-Assad regime, and how does the U.S. fit into that picture? (Jason Aldag/The Washington Post)

Sectarian violence is likely to continue in Syria long after the fall of President Bashar al-Assad as divisions among opposition groups deepen, the Obama administration’s top intelligence official said Thursday.

“The most likely scenario that we see, even after Assad falls, is probably more fractionalization, if I can use that word, both geographically and on a sectarian basis, for some period of time . . . at least a year, a year and a half,” Director of National Intelligence James R. Clapper Jr. told the House Permanent Select Committee on Intelligence.

Clapper said Islamist extremist groups within the opposition remain powerful far beyond their actual numbers and “have a presence in 13 of the 14 provinces in Syria.”

“Their numbers themselves are not indicative of their real influence,” he said.

Asked to quantify the likelihood that the United States and its allies would be able to secure Syria’s chemical weapons arsenal if Assad falls, Clapper declined. “I’m not sure I know how to make a call like that,” he said, adding without elaboration that it “would be very, very situationally dependent.”

A look at the Syrian uprising nearly two years later. Thousands of Syrians have died and President Bashar al-Assad remains in power, despite numerous calls by the international community for him to step down.

The administration has repeatedly expressed concern that such weapons could fall into the hands of extremists. Other officials have said that current plans do not include insertion of U.S. troops to secure chemical munitions.

At a separate hearing, Defense Secretary Chuck Hagel told the House Armed Services Committee, “We have not detected use of chemical weapons. . . . Obviously, if that line is crossed, then we’ve got a different situation. Then you get into the next set of dimensions to this, if chemical weapons fall into the wrong hands.”

Lawmakers across Capitol Hill voiced increasing frustration over the worsening situation in Syria, though they remained divided on what to do about it. More than 70,000 people have died in the two-year-old civil war there, and millions have fled their homes.

The number of Syrian refugees in neighboring countries, estimated at 1.3 million, “could double or even triple by the end of 2013. That would amount to nearly one-third of Syria’s population,” A. Elizabeth Jones, the acting assistant secretary of state for Near Eastern affairs, told the Senate Foreign Relations Committee.

Although some senators voiced concern about any expansion of the U.S. role in Syria beyond humanitarian assistance, Sen. John McCain (R-Ariz.) repeated his call for American military involvement, disputing an assessment by U.S. Ambassador Robert Ford that opposition leaders would like more assistance but are “appreciative” of the humanitarian aid they have received.

“I’ve met with the [opposition] military leadership, I’ve been to the refu­gee camps,” McCain said. “They’re not appreciative, they’re angry and bitter.”

Meanwhile, a meeting of foreign ministers of the Group of Eight nations in London ended without agreement on Syria, as Russia refused to relinquish its backing for Assad.

“Have we solved that division at this meeting? No. We didn’t expect to do so,” British Foreign Secretary William Hague told reporters.

In a statement Thursday, Russia’s Foreign Ministry said it shared the concern of others that al-Qaeda could turn Syria “into their main springboard in the Middle East.” But Moscow did not yield on its insistence that political negotiations among the opposing parties precede any decision on Assad.

“Russia will continue to resist putting more international pressure on Syria or Iran,” Clapper told the intelligence committee. Iran and Russia are the primary suppliers of weapons to the Assad government.

Those G-8 countries that are aiding Syrian rebels, including Britain, France and the United States, met privately with opposition leaders but deflected their request to provide weapons. Instead, the countries indicated that they would increase non­lethal military aid to the rebels.

The Obama administration said last month that it would send food and medical assistance to the rebel military, and President Obama issued orders Thursday to make $10 million worth of supplies available.

Obama and other senior administration officials also met this week with Peter Maurer, president of the International Committee of the Red Cross, who said he urged them to use U.S. influence to persuade fighters on both sides in Syria to allow the distribution of humanitarian aid.

Human rights violations “happen on both sides” of the conflict, Maurer said in a meeting with Washington Post reporters. “Both are threatening and killing doctors and nurses from the other side” and preventing aid from reaching those they view as political or sectarian opponents, he said.

Amid a total breakdown of social norms and services, Maurer said, “we may soon be in a situation where we lose control of what is happening, and the consequences may be much more difficult to imagine.”