UPDATE 2-Mediators work to salvage Russia-Georgia talks

* Mediators struggle to salvage talks, regret walkout

* Russia pulls out of security talks with Georgia

* Russian foreign minister Lavrov says awaits UN report

* Georgia delegation says hopes talks resume on Tuesday

(recasts with cochairs' statement, quotes, changes dateline)

By Stephanie Nebehay

GENEVA, May 18 (Reuters) - International mediators struggled to salvage the latest round of security talks between Russia and Georgia on Monday after Moscow's delegation walked out.

Delegations from Russia and the Moscow-backed rebel region of South Ossetia withdrew from the Geneva talks, citing the refusal of another Moscow-backed rebel region, Abkhazia, to attend, due to a delay in a U.N. report, both sides said.

But Russian Foreign Minister Sergei Lavrov indicated that Russia could rejoin the two-day talks on Tuesday if U.N. Secretary-General Ban Ki-moon issues that report on its operations in the Abkhaz region. The U.N. chief is in Geneva.