The horror in Paris, coming just weeks after the downing of a Russian jetliner in Egypt, underscores the risks of a strategy that relies heavily on local forces to defeat the Islamic State with American backing.

The core of President Obama’s strategy is using U.S. military air power to contain and degrade the Islamic State until local forces are ready to take the fight to the group. It’s an approach that acknowledges the president’s reluctance to be drawn into another major ground war in the Middle East and his belief that U.S. military power can’t by itself secure a lasting victory in Iraq and Syria.

The Paris attacks suggest that the Islamic State and its affiliates may have a broader reach and pose a deadlier threat to the West than intelligence officials and the Obama administration had previously believed to be the case.

Just hours before coordinated teams of gunmen killed more than 120 people in Paris, Obama, in an interview with ABC News, described the campaign against the Islamic State as a “multi-year project” that had succeeded in its initial goal of containing the group.

The Paris attacks could force the president to adopt a strategy that is more focused on destroying the group’s global reach beyond Iraq and Syria.

Some administration officials have argued that the United States, while the campaign in Iraq and Syria grinds on, must do more to address threats from Islamic State affiliates in places such as Libya, the Sinai Peninsula and Yemen. They also call for more steps to stop Islamic State fighters and money from moving across borders, and to better understand how the group’s core leadership in Iraq and Syria communicates with other nodes.

Such measures have been on the White House’s agenda for months but have largely taken a back seat in internal debates that have focused on stopping the Islamic State in Iraq and Syria.

“What makes the Islamic State especially virulent is the ability of the center to support and communicate with the branches,” said a senior administration official, who, like others, spoke on the condition of anonymity to discuss U.S. strategy.

U.S. officials say that in recent months, they have detected some progress in the campaign against the Islamic State in its Iraq-Syria base.

Kurdish and Arab rebels aligned with the United States have cleared some areas of northern Syria. As part of a recently approved set of new measures, the U.S. military is now providing intensified air support and limited weaponry to help them prepare for an eventual assault on Raqqa, the Islamic State’s de facto capital.

This past week, an airstrike appeared to have killed Mohammed Emwazi, or “Jihadi John,” the British militant who executed Western hostages. In Iraq, Kurdish peshmerga forces are now fighting to solidify control of Sinjar, a strategically located town.

Peter Finn, The Washington Post's national security editor, explains how the Paris attacks illustrate how the Islamic State has evolved as a terror organization. (Thomas Johnson, Monica Akhtar and Julio Negron/The Washington Post)

Administration officials described the battlefield additions as incremental boosts to a strategy that remains focused on slowly degrading the Islamic State in its heartland and continuing the slow process of building up local forces that can ultimately defeat the group.

“Our goal has to be to recruit more effective partners in Iraq to really go on offense,” Obama said in the ABC interview prior to the Paris attacks.

But the administration has taken only limited steps to address the rise of Islamic State activities beyond those two countries, even as militant groups identifying themselves with the group crop up from Nigeria to Pakistan.

In Afghanistan, affiliated militants have used tactics shocking even in a country accustomed to brutality. In Egypt, officials are trying to determine whether the group’s affiliate there was responsible for the downing of the Russian airliner last month.

While U.S. officials have expressed skepticism that those groups are under the direct command and control of Islamic State leaders in Iraq and Syria, they believe the Libya affiliate — the strongest yet — is. On Friday, U.S. aircraft launched a strike against Wisam al-Zubaidi, who American officials described as the Islamic State’s leader in Libya.

The strike may be an indication of what U.S. officials have described as their plan for mitigating the risks of their slow-and-steady approach: using targeted counterterrorism tools, including raids and airstrikes, to address direct threats when they appear.

A senior defense official said the strike near Derna, a militant hotbed in Libya, “shows that we do have an ability to target their leadership while they are aspiring to do more and to grow.”

Brian Katulis, a senior fellow with the Center for American Progress, said the Paris attacks underscore the limits of that approach, especially in “an era of pop-up jihadis and crowd-sourced” attacks. “We can take leaders off the battlefield, but it doesn’t produce an environment of sustainable security where these threats are pushed to the margins. . . . It’s a recipe for perpetual light-footprint war.”

Officials say it’s too soon to say whether the Paris attacks will alter the U.S.-led military campaign in Iraq and Syria. Although France has conducted the second-largest number of airstrikes after the United States, it ranks a distant second. Arab allies’ military participation, small from the beginning, dropped off following the start of a separate Saudi-led campaign in Yemen.

Defense Secretary Ashton B. Carter, who spoke with French Defense Minister Jean-Yves Le Drian on Saturday, has been working in recent months to expand European participation in the military campaign, defense officials said.

Julie Smith, a former White House official now at the Center for a New American Security, said that although Friday’s attacks may prompt an increased military response from some European nations, that reaction is less likely from countries that don’t perceive a direct threat.

It’s still not clear whether the eight attackers, all of whom are dead, were directed by the core Islamic State leadership or were merely inspired by calls for violence against the West. In a meeting Saturday with his national security team, Obama was told that the United States had “no information to contradict the initial French assessment” of Islamic State responsibility.

If the attackers didn’t receive direct orders, it would be an indication of a more widely dispersed campaign that will pose major challenges to Western security agencies.

“It’s very hard to have a military war against ideology,” a senior defense official said. “With al-Qaeda, we learned and they learned that having a centrally directed operation is something we can go after. But it becomes much harder to do that when it’s a simple ideology.”

For the foreseeable future, the threat of small-scale or copycat attacks will put a major burden on intelligence agencies to detect operations in advance.

“Anyone who’s been in that business knows that it’s almost impossible to score 100 percent,” said Bruce Riedel, a former CIA and White House official. “So we’re in for a long haul here.”