WASHINGTON - A U.S. military patrol has blocked a Russian military convoy from using a main highway in northeast Syria amid growing tensions between the two sides, local reports said.

The Syrian Observatory for Human Rights, a war monitor that has researchers inside the country, reported on Tuesday that U.S. forces didn't allow Russian military vehicles to use a major road between two Kurdish-held towns in Syria's northeast.

The Russian convoy was attempting to reach a border crossing between Syria and Iraq that is under the control of U.S.-backed Syrian Democratic Forces (SDF), the Observatory added.

After Turkish military and allied Syrian militias launched an offensive against SDF fighters in October 2019, Russia, a staunch supporter of Syrian President Bashar al-Assad's regime, stepped in to increase its military presence in northeast Syria following a U.S. decision to withdraw troops from parts of the border area between Syria and Turkey.

After mounting pressure from the U.S. Congress and U.S. foreign allies, President Donald Trump decided to keep about 500 U.S. troops in the area to protect the region's oil fields, and prevent Islamic State and Syrian regime troops from accessing them.

Now, both the U.S. and Russia have military outposts throughout the region.

Growing tensions

The incident on Tuesday is part of a series of similar incidents that happened in recent days between the two powers over their presence in Syria, local sources said.

"This is the third incident that occurred within a week," said Nishan Mohammad, a local reporter who said he witnessed another recent standoff between U.S. and Russian troops in northeast Syria.

"I was there last weekend when U.S. soldiers stopped Russian military vehicles and forced them to head back to their base," he told VOA in a phone interview Tuesday.

It seems that the U.S. wants to limit the Russian presence in certain parts of northeast Syria, Mohammad added.

Contacted by VOA, SDF officials declined to comment on the matter, citing the sensitivity of the issue.

U.S. and Russian officials have not immediately reacted to this development.

Reasserting Assad's authority

Northeast Syria has largely been under the control of Kurdish forces since 2012 after Syrian regime troops withdrew to focus on fighting rebel forces elsewhere in the war-torn country.

With Syrian troops now in control of most territory once held by rebels, experts charge that Russia's recent moves in northeast Syria are an attempt at reasserting the Syrian government's authority in that region."

Russia's clear objective is to reestablish the authority of the (Syrian) regime in the Kurdish region," said Radwan Badini, a Syria expert who teaches journalism and politics at Salahaddin University in Irbil, Iraqi Kurdistan.

He told VOA that such provocations by Russia will not yield any results in Moscow's favor, as Syria's northeast is of strategic importance to the U.S. in its continued war against IS.

"The Americans will not give up this part of Syria," Badini said, noting that, "in addition to its oil fields, northeast Syria represents a strategic depth for the U.S. and its allies to carry on their counterterrorism efforts in eastern Syria."