The Russian defense minister has proposed that Russia and the U.S.-led coalition launch joint action 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 suggested that, starting from that date, Russia and the U.S.-led coalition conduct 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.