The U.S. military has had to divert its flight paths over Syria because of competing Russian combat flights there, the Pentagon said Wednesday.

In “at least one instance,” the U.S. military had to conduct a “safe maneuver,” Navy Captain Jeff Davis told reporters. The intent was to “ensure the separation of aircraft.” A senior defense official told The Daily Beast that the interaction happened two days ago when a Russian flight came within 20 miles of a manned U.S. aircraft flying over eastern Syria. The self-proclaimed Islamic State dominates much of northeast Syria.

That Russian flights were over eastern Syria suggests that Russia is conducting military movement in territory under the ISIS control, despite U.S. assertions that Russia’s focus is on other opponents to the current Syrian leader.

Russia’s main airstrip in Syria is in the western city of Tartous. That is, there is no flight path that would require Russian aircraft to fly over the east.

Since Russian airstrikes began last week, U.S. and Russian officials have discussed ways to “deconflict,” a term that refers to ways that Russian and U.S. aircraft do not mistakenly cross paths, or fire on one another or allies on the ground. But there have only been two conversations with Russian defense officials, and it appears the U.S. is making adjustments in lieu of a formal agreement between the two countries.

The U.S. military is adjusting flight plans any time there is a prospective risk, defense officials said.

“We are making sure we are not going to have any inadvertent air incident,” a senior defense official told The Daily Beast.

But the military maneuver counters statements by the Defense Secretary Ash Carter just hours earlier about how the U.S. is responding to Russian airstrikes inside Syria. While speaking to troops in Sigonella, Italy on Wednesday, Carter said the U.S. was “ignoring” Russia’s intervention in Syria, which has focused on opponents to Syrian President Bashar al-Assad that are not ISIS. Such strikes could help the Syrian leader retain his hold on western parts of the country.

“We are gonna keep on doing what we are doing, unchanged,” Carter said, adding. “We are going to ignore them.”

— Nancy A. Youssef