Tom Vanden Brook

USA TODAY

WASHINGTON — President Trump has authorized the Pentagon to arm Kurdish forces fighting the Islamic State with "medium" size weaponry, a move certain to cause friction with NATO ally Turkey, U.S. officials said Tuesday.

The Kurds have been among the most effective and reliable ground forces since the U.S.-led coalition launched its air war against Islamic State, or ISIS, militants in Iraq and Syria in 2014. However, Turkey considers some Kurdish groups to be terrorists and has opposed giving them weaponry.

The arms include machine guns, mortars, rifles and ammunition, according to a U.S. official familiar with the plan but authorized to speak about it publicly.

Arming the Kurds is seen by the Pentagon as key to retaking the Syrian city of Raqqa, which ISIS considers its capital. The Syrian Democratic Forces, which include Kurd and Arab fighters, would be on the ground.

"The SDF, partnered with enabling support from U.S. and coalition forces, are the only force on the ground that can successfully seize Raqqa in the near future," Dana White, the chief Pentagon spokesman, said in a statement.

At the White House, spokesman Sean Spicer said the move is designed "to assure a clear victory over ISIS" in Raqqa.

However, Kurdish YPG fighters, who will be receiving the weapons, are considered by Turkey to be terrorists.

"We are keenly aware of the security concerns of our coalition partner Turkey. We want to reassure the people and government of Turkey that the U.S. is committed to preventing additional security risks and protecting our NATO ally," White said in a statement.

U.S. officials have assured officials from Turkey that they will work to "prevent additional security risks" to their country, Spicer added.

YPG fighters likely have received a limited amount of arms and ammunition through the SDF, the official said. The change in policy will arm them with enough weaponry to fight entrenched ISIS forces in Raqqa.

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Contributing: David Jackson