(CNN) US forces in Syria have increased surveillance of Russian troop locations following Moscow's suggestion that US troops could get caught in Russian military operations, according to a US official directly familiar with US military planning.

While the US has kept a close eye on Russian troop locations for the past several months, the need for increased surveillance has become critical given the proximity of US and Russian units in eastern Syria.

The goal is to ensure that US forces continue to know the location of Russian forces, especially those in eastern Syria, at all times, said the official, who declined to be identified because of the sensitivity of the matter. Surveillance and reconnaissance levels routinely fluctuate based on threats.

For now the military assesses that the Russians don't intend to attack US forces and that much of the rhetoric is politically driven. However, officials acknowledge they are a worried that a misunderstanding or poor Russian military skills could lead to an incident -- concerns that are driving the decision to boost surveillance.

"We always know where they are," the official said of the Russians.

The uptick in surveillance is separate from any increased force protection measures for US forces. It comes amid daily discussions with the Russians about both sides deconflicting air and ground operation areas.

US Army Col. Ryan Dillon, a spokesman for the coalition, told reporters Thursday that coalition military planners had not increased their force protection measures after Saturday's airstrike against US-backed fighters in Syria, despite the proximity of the attack to US special operations forces.

"We have always maintained the capabilities and the over-watch both from the air and forces on the ground," Dillon said, adding, "I would not say there's been an increased amount of force protection measures. I would say that it is where it needs to be and it has been so from the beginning."

The surveillance boost also comes just days after coalition and Russian generals met in an unprecedented face-to-face meeting to share greater detail about each side's operations, in part to avoid incidents like what happened last week, when a Russian warplane bombed US-backed Syrian Democratic Forces with US troops nearby.

The Russian Ministry of Defense issued a warning Thursday that its forces would retaliate against the US-backed Syrian Democratic Forces and their US military advisers if any of their forces accompanying Syrian regime troops come under attack. The ministry issued a statement saying that already "the Syrian Democratic Forces and US Special Operations Forces have twice targeted Syrian troops with mortars and rocket artillery."

Asked about the Russian warnings during a press appearance before a meeting with the Polish minster of defense at the Pentagon, Secretary of Defense Jim Mattis said the recent events did not cause him concern.

"I am not worried. We continue to deal with the Russians in a collaborative way," Mattis said. "We'll sort this out."

The two sides are coming ever closer raising the prospect of additional clashes.

While Syrian regime forces had primarily operated on the western side of the Euphrates River and SDF forces on the eastern side, the Russian Ministry of Defense issued a statement Monday saying regime troops, backed by Russian air power, had crossed over to the river's eastern bank near the city of Deir Ezzor, bringing them closer to an SDF offensive targeting ISIS elsewhere in the province.

The SDF issued a statement Saturday saying its fighters had captured the Conoco gas field in southeastern Syria, a major economic and strategic location.

Russia's Ministry of Defense issued a statement Sunday saying the rapid SDF advance was due to the absence of any resistance from the ISIS fighters in the area, suggesting that SDF fighters and their US advisers had made some sort of arrangement with ISIS.

"Facing no resistance of the ISIS militants, the SDF units are advancing along the left shore of the Euphrares towards Deir Ezzor," the statement said, later adding "this suggests that the US troops feel safe in terrorist controlled regions."

The tensions between the two sides risks undermining the campaign against ISIS in the Middle Euphrates River Valley, where US officials believe the terrorist group has housed much of its leadership as well as up to 10,000 of its fighters.