The Obama administration has loosened the rules of engagement for U.S. forces striking the Islamic State and affiliated groups in Afghanistan, allowing them to target militants just for being associated with the terror network, a senior defense official confirmed to Fox News.

The new authorization now puts ISIS in the same category as al-Qaida in Afghanistan.

Previously, the militants could be targeted only if they showed what's known as hostile intent.

"Now," a U.S. official told Fox News, "we can kill ISIS in Afghanistan just for wearing the T-shirt or waving their flag."

The Wall Street Journal first reported the change.

The development comes after the State Department designated the affiliate "ISIL-K," or Khorasan, as a foreign terrorist organization earlier this month.

Despite the new authorization allowing the military to more easily target ISIS supporters, the U.S. has been going after the militants in Afghanistan for months.

The U.S. military has conducted dozens of drone operations against ISIS affiliates in eastern Afghanistan beginning this summer in order to protect Afghan, U.S. and foreign forces.

-- Lucas Tomlinson is the Pentagon and State Department producer for Fox News Channel.

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