The Russian defense minister has proposed that Russia and the U.S.-led coalition launch joint airstrikes against the al-Qaida-linked Nusra Front in Syria.

Defense Minister Sergei Shoigu said Friday that Moscow had proposed to Washington that they encourage all militants willing to abide by a cease-fire in Syria to leave areas where Nusra is present before May 25.

He said Moscow has proposed that Russia and the U.S.-led coalition would then begin joint strikes against Nusra and any other groups refusing to honor the truce.

The U.S.-Russia-brokered cease-fire has helped reduce violence in Syria, but it has been steadily eroding. The Islamic State group and the Nusra Front have been excluded from the cease-fire, and Russia long has pushed for excluding other militant groups that have cooperated with Nusra.

The proposal, which would still need the backing of the U.S. government and its allies, comes at a time of rising tensions between Russia and NATO.

Nearly simultaneous with the Syrian proposal, Shoigu announced that his nation’s military has strengthened forces in the southwestern region with long-range weapons to fend off emerging new threats.

Shoigu said Friday the move was taken in response to “attempts by some nations to expand their military presence near our borders,” an apparent reference to NATO.

Shoigu said that troops of the Southern Military District have been beefed up with “precision long-range weapons” and air defense. He added that the Russian navy potential in the region has increased by one-third.

Amid Russia-West tensions over the Ukrainian crisis, the U.S. has sent additional military equipment to the Baltics and Central Europe. Last week, a U.S. missile defense site also became operational in Romania. Russia has threatened to take retaliatory steps to maintain a strategic parity.