WASHINGTON, Nov. 21 (Xinhua) -- U.S. Defense Secretary James Mattis said on Wednesday that the U.S. military is building observation posts along the Turkey-Syria border, widely seen as a move to reduce tension with Turkey.

"We are putting in observation posts in several locations up along the Syria border, northern Syria border," Mattis told reporters at a Pentagon briefing.

He said that the United States would like to be the one warning the Turkish side when "something is coming out of an area that we're operating in."

"We are consulting closely with Turkey," the Pentagon chief added.

The United States currently has about 2,000 troops serving in Syria, assisting local forces against the Islamic State (IS) militants, according to U.S. media reports.

Washington has been backing the Kurdish-led Syrian Democratic Forces (SDF) for a long time in the battles against the IS. However, Turkey, which has for long been outright about its enmity to the Kurdish forces, said it was ready to launch offensives against the Kurds on the eastern side of the Euphrates River.

The Turkish forces have actually started shelling positions of the Kurdish-led forces in northern Syria, pushing the U.S.-backed SDF to slow down on its second stage of battles against the IS.

To ease the tension, the United States deployed forces along the line between the two sides of the Euphrates River earlier this month to contain the situation, according to a report from a Syrian human rights group.

In general, the U.S.-Turkey ties are undergoing a recovery process after a dispute over Turkey's detention and trial on terrorism charges of U.S. pastor Andrew Brunson, who was released by Turkey last month.