UPDATE 1-Lithuania ready for lone stand on EU-Russia talks

(Adds Slovenian spokesman, diplomat, details)

By Nerijus Adomaitis

VILNIUS, April 25 (Reuters) - Lithuania is prepared to take a stand against the rest of the European Union to try to tighten the terms of an EU mandate for partnership talks with Russia, the country's foreign minister said on Friday.

EU President Slovenia wants a mandate to be rubber-stamped by foreign ministers of the 27-member bloc in Luxembourg next Tuesday, allowing negotiations with Moscow on a wide-ranging pact to begin by the time of an EU-Russia summit in June.

But ex-Soviet Lithuania is demanding any mandate include assurances on energy supplies, Russian cooperation over a missing Lithuanian businessman, and movement by Moscow on unresolved 'frozen conflicts' in former Soviet republics.

Some EU envoys said a deal was in sight after Slovenia offered ideas for a compromise on Thursday. A Slovenian foreign ministry spokesman said the stand-off was now being discussed "at the highest level".

But Lithuanian Foreign Minister Petras Vaitiekunas said he would insist the issue be dropped from the agenda of Tuesday's meeting unless its demands were fully met.

"I have told Slovenia that I will demand taking the issue of a mandate off the agenda of the EU foreign ministers' meeting," he told the Lithuanian parliament's European Affairs committee.

"That is going to be an open confrontation with the EU Presidency, as well as with the other EU member states."