Presidential hopeful Sen. Bernie Sanders expressed concerns with President Barack Obama’s decision on Friday to deploy a small number of U.S. special operations forces in northern Syria to fight ISIS, saying he fears the country “being drawn into the quagmire of the Syrian civil war.”

The Vermont lawmaker said in a statement through a spokesman Michael Briggs on Friday that the U.S. involvement “could lead to perpetual warfare.”

“The senator believes that the crisis in Syria will be solved diplomatically, not militarily,” the statement reads.

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President Obama’s decision is a major shift for him, as he has long said he has no desire to put U.S. troops in Syria’s bloody conflict. He has authorized fewer than 50 commandos to deploy into northern Syria. They will work with moderate opposition forces who are fighting the militants.

White House spokesman Josh Earnest said that the troops will be there in a “train, advise and assist mission” — and not in a combat role. He added that the move is an “expansion” but not a “change” in U.S. strategy against ISIS.

Sanders, a self-described “democratic socialist,” who is seeking the Democratic Party’s nomination, supports for efforts by Secretary of State John Kerry to include bring Iran, Saudi Arabia, Russia and other nations into discussions on how to end the civil war, the spokesman added.

On the campaign trail, Sanders has said he is not opposed to using military force, but he believes it only should be used as a last resort.

A spokesman for former secretary of state Hillary Clinton, Sander’s chief rival, told CNN that the former first lady “sees merit in the targeted use of special operations personnel to support our partners in the fight against ISIS, including in Syria.”