A man inspects a damaged Civil Defence station in the rebel held town of Atareb, Aleppo countryside, Syria, April 26, 2016. REUTERS/Ammar Abdullah

Russia's United Nations Ambassador Vitaly Churkin urged the U.N. Security Council Wednesday to blacklist two powerful Syrian rebel groups who are conducting terrorist activities and not observing the cessation of hostilities in Syria. Russia considers the hard-line Islamic groups — Jaish al-Islam and Ahrar al-Sham — as "terrorist organizations."

Churkin reportedly said that the groups, one of which is playing a key role in political negotiations aimed at ending the five-year civil war in Syria, should be subjected to sanctions. U.N. diplomats reportedly said that the proposal to the council's Islamic State and al Qaeda sanctions committee will go into effect on May 11 only if other nations that are part of the 15-member committee don't block it.

"The reason for such a move was the information that these groups, which are waging a war in Syria, are closely connected to terrorist organizations, first of all with [Islamic State group] and al Qaeda," Churkin reportedly said.

Edgar Vasquez, a spokesman for the U.S. mission, cautioned against blacklisting the two groups, saying: "Designating Jaish Al-Islam and Ahrar Al-Sham — two groups that are parties to the cessation of hostilities — would have damaging consequences to the cessation just as we are trying to deescalate the situation on the ground."

A U.N. diplomat told Reuters that Russia aims to divide the opposition to support its long-term ally Syrian President Bashar Assad.

Russia increased its military presence in Syria in September to defeat the Islamic State group and other “terrorists.” However, several countries have argued that Russia’s attack in Syria is intended at keeping Assad in power. The Syrian government often refers to all opposition fighters as "terrorists."

Mohammed Alloush, a leading figure in Jaish al-Islam, heads the High Negotiating Committee, the main opposition umbrella group at the Geneva peace talks that are largely stalled. The Syrian government has consistently criticized the group's representation at the peace talks.