MOSCOW (Reuters) - Russia said on Thursday the Syria ceasefire process was underway despite what it said were attempts by some U.S. officials to sabotage it, while reiterating that Russian warplanes would continue pounding what it called terrorist groups.

Residents inspect damage after an airstrike on the rebel held al-Fardous neighbourhood of Aleppo, Syria February 18, 2016. REUTERS/Abdalrhman Ismail

The “cessation of hostilities” agreed by the United States and Russia is due to take hold on Saturday morning from midnight. Damascus has agreed to the deal, as has the main opposition alliance, though it is only ready to commit for two weeks given its deep reservations.

Russian Foreign Ministry spokeswoman Maria Zakharova said “some U.S. officials” had tried to “sabotage” the ceasefire plan “by interpreting it from such cardinally different points.”

“By and large, a number of (U.S.) officials in fact attempted to call into question the agreements reached, which were approved by the two presidents,” she told a news briefing on Thursday. “It actually looked like sabotage.”

Commenting on the current state of interaction with Washington, she said: “We are in contact with American officials, the process is underway and is very active... We have an exchange of information, our military are in contact.”

Officials in Moscow have been unnerved by a statement by U.S. Secretary of State John Kerry shortly after the ceasefire plan was reached that Washington was also considering an unspecified “Plan B”.

There is no “Plan B” on Syria’s ceasefire and will not be one, RIA new agency quoted Russian Foreign Minister Sergei Lavrov as saying.

The cessation of hostilities plan does not include Islamic State or the Nusra Front, an al Qaeda affiliate that is widely deployed in opposition-held areas. The opposition has expressed fears government forces backed by the Russian air force will continue to attack rebels under the pretext of targeting Nusra.

Zakharova hit out at unspecified “Western media creating an impression ... that Russia will stop its operation against Islamic State, the Nusra Front and other terrorist groups”.

“There was no talk of ending the fight against terrorism, there is no such talk and there won’t be any,” she said.