Sochi: Russia and Turkey remained at odds over a threatened assault by Russian-backed regime forces on the last major rebel bastion in Syria as President Recep Tayyip Erdogan and Russian counterpart Vladimir Putin prepared to meet in the Black Sea resort of Sochi.

“The situation with Idlib is acute,” President Putin’s spokesman, Dmitry Peskov, said on Monday, state media reported. “There are differences in our approach.”

Erdogan urged against using “pretexts” for military action in the northwestern Syrian province, while saying he backs joint steps against “terrorists,” according to Hurriyet newspaper.

Monday’s will be the second meeting between the two leaders in less than two weeks. Russia and Iran, the two allies of Syrian President Bashar Al Assad, clashed with Turkey at a summit on September 7 in Tehran, rejecting Erdogan’s call for an immediate ceasefire in Idlib. Still, amid a Turkish military build-up inside Syria to deter an attack on rebels there, regime troops have held back from a full-scale offensive.

The US has warned Assad and Russia against launching an assault and threatened to retaliate if regime forces use chemical weapons.

Almost 3 million civilians live in Idlib and fighting could provoke a massive new exodus of refugees to Turkey. There are tens of thousands of rebels in the region with reported ties to Turkey as well as an estimated 10,000 Jihadist fighters linked to Al Qaida.