MOSCOW/WASHINGTON, Dec. 13 (Xinhua) -- Russia and the United States have blamed each other for the recent fall of the ancient Syrian city Palmyra into the hands of the Islamic State (IS) militants.

Kremlin Spokesman Dimitry Peskov on Monday regretted the failure to stop the IS offensive in Palmyra, as well as the lack of coordinated action and real cooperation with other states that are unwilling to cooperate, the United States first and foremost.

"This cooperation was likely to enable us to avoid similar attacks of terrorists," Tass news agency quoted the spokesman as saying. Peskov also expressed the hope that the IS would be forced out of Palmyra soon.

"What is happening around Palmyra is further evidence that the threat from the IS is serious," Peskov said and reaffirmed that Russia would continue its anti-terrorist operations in Syria. ' Later in the day Russian Foreign Minister Sergei Lavrov said the IS attack on Palmyra might be part of a conspiracy to recharge Syrian rebels.

"It makes me think, and I hope I am wrong, that it is all orchestrated in order to give a respite to the bandits still in eastern Aleppo," Lavrov said during a press conference as he visited Serbia.

The minister also accused the United States of its "dead-end position" and double standards in negotiations on Syrian issues, urging Washington to persuade armed rebels to lay down weapons and leave Aleppo.

The U.S. side however blamed Russia for its failure to sustain the "singular gain" against IS since Moscow's military intervention started in September 2015.

"This is a further demonstration of why, as we have long advocated, Russia must change its focus," the AFP quoted a Pentagon spokesman as saying.

The IS succeeded in retaking Palmyra on Sunday in a major offensive that had started Thursday. The historical sites in the city had been largely destroyed as the terrorist group had controlled the city in 2015 but was driven out by the Syrian army this March.

Russia and the United States have long been at odds over the peaceful settlement of the Syrian crisis.

Recently Western countries proposed a resolution at the United Nations Security Council regarding a truce in Aleppo, which was vetoed by Russia and China and criticized by Damascus as a so-called humanitarian pause would only give rebels a chance to regroup and empower themselves.