Afghan National Army (ANA) officers participate in a training exercise at the Kabul Military Training Centre in Afghanistan, in this October 7, 2015 file photo. In 2015, the Afghan army had to replace about a third of its roughly 170,000 soldiers because of desertions, casualties and low re-enlistment rates, according to figures released by the U.S. military in December. REUTERS/Ahmad Masood/Files

The Obama administration has granted the military new authorities to strike the Islamic State in Afghanistan, signaling a more sustained fight against the extremist group outside of its base in Iraq and Syria, officials said on Wednesday.

A defense official, speaking on condition of anonymity to discuss internal decisions, said new rules of engagement approved last week permitted commanders in Afghanistan to launch air strikes against Islamic State militants because of their affiliation with the group, in the same way it targets fighters linked to al-Qaeda.

The new arrangement “enables the United States to more actively target ISIL in Afghanistan,” the official said, using an acronym for the group that controls much of Iraq and Syria and has established outposts from North Africa to central Asia.

Under previous rules, the U.S. military was able to conduct air strikes in Afghanistan in three circumstances: to protect foreign forces; to help Afghan troops ward off an enemy onslaught; and to target al-Qaeda and affiliated militants.

According to a second official, who also spoke on condition of anonymity, the U.S. military has struck militants identified with the Islamic State in Afghanistan in the past, but those strikes were launched on the basis of the fighters’ “hostile intentions” rather than their affiliation with the group’s Afghanistan cell. The new rules were first reported by the Wall Street Journal.

While the decision does not signal a dramatic change for U.S. activities in Afghanistan, it strengthens commanders’ authority against assorted militants there and, more generally, is another illustration of the expanding U.S. campaign against the Islamic State beyond its home base.

The change comes as the Afghan government struggles to beat back an emboldened Taliban, whose sustained attacks have jeopardized not just ordinary Afghans but President Obama’s hopes to end U.S. military involvement in Afghanistan before he leaves office. The White House has already altered Obama’s original plans for withdrawing U.S. troops several times amid worsening security across Afghanistan.

Now, the country faces a new threat from militants who have aligned themselves with the Islamic State and who are mostly arrayed near Afghanistan’s border with Pakistan. Defense Sec. Ashton Carter visited eastern Nangahar province in December and discussed the growing Islamic State presence there with Gen. John F. Campbell, the commander of U.S. and NATO forces in Afghanistan.

Taliban and Islamic State forces are now battling one another for control of resources, even as both stand off against government forces.

The decision follows the U.S. State Department’s designation this month of the Islamic State’s Afghanistan cell, called “ISIL-K,” or Khorasan, as a foreign terrorist organization.