* Says radicals strengthening positions
* Criticises U.N. monitors in Syria
By Steve Gutterman
MOSCOW, Oct 1 (Reuters) - Russia expressed doubt on Tuesday that Western nations can persuade Syrian opposition representatives to take part in an international peace conference in time for it to take place in mid-November.
The doubts of Damascus's most important ally followed remarks in which the international envoy for Syria, Lakhdar Brahimi, said the target date of mid-November was "not 100 percent certain" and cited disunity among rebel forces.
"Until recently we hoped our Western partners, who undertook to bring the opposition to the conference, could do it quite quickly, but they were unable to do it quickly, and I don't know whether they will be able to do so by mid-November," Russian Foreign Minister Sergei Lavrov said.
A pledge by the Syrian government to abandon chemical arms has increased prospects for the peace conference, proposed by Russia and the United States in May, to go ahead.
U.N. Security Council powers hope it can be held in mid-November. Lavrov said it must be organised soon since "radicals and jihadists are strengthening their positions" in Syria.
"The task is to not lose any more time, and to bring to the negotiating table with the government those opposition groups that ... think not about creating a caliphate in Syria or just seizing power and using it at their will, but about the fate of their country," Lavrov said after meeting Ekmeleddin Ihsanoglu, secretary general of the Organisation of Islamic Cooperation.
Lavrov also called into question the thoroughness of a U.N. chemical weapons mission after suggesting that it had not examined a site outside of Aleppo where Russia and the Syrian government say rebel forces likely used chemical weapons.
"The commission recently returned (to Syria) and already announced that it finished its work and is returning to New York," said Lavrov.
"As far as I understand, they examined several more places where there are claims chemical weapons were used near Damascus. And as before, the commission did not travel to the outskirts of Aleppo, where a serious incident of the use of chemical weapons occurred on March 19."
Syrian rebels blame Assad's government for that attack.
Russian experts visited the location earlier this year and took samples of material from the site that were later analysed at a Russian laboratory certified by the Organisation for the Prohibition of Chemical Weapons, Russia's U.N. envoy said previously.
The site was one of the places covered in the U.N. committee's mandate. "And so we want to understand whether the mission's report will be complete or incomplete," Lavrov said, "considering that this mission was not able to visit all the locations named in its initial mandate."