VIENNA (Reuters) -A Russian court ruled on Monday that Russian investment company Rasperia could enforce a $2.1 billion claim against the assets of Austrian lender Raiffeisen Bank International's Russia unit over a planned share purchase Raiffeisen had abandoned.

RBI has been under pressure from European and U.S. authorities, particularly since Russia's full-scale invasion of Ukraine, to spin off its Russian business, and it has long said it plans to do so but that still has not happened.

It must tread carefully to avoid falling foul of international sanctions against Russia or angering Moscow to the point that it punishes RBI in Russia.

RBI attempted last year to unlock some of its frozen Russian funds by using them to buy a roughly $1.6 billion stake in Austrian construction company Strabag from Rasperia, which had been controlled by Russian tycoon Oleg Deripaska, who was under U.S. and European Union sanctions.

Rasperia's ownership later changed but Raiffeisen still walked away from the deal in May, saying it had "been unable to obtain the required comfort in order to proceed with the proposed transaction".

Rasperia brought legal action in Russia against RBI.

"The court has decided that STRABAG SE and its Austrian core shareholders are liable to pay 2.044 billion euros ($2.12 billion) to Rasperia and that the verdict can be enforced against (RBI Russian unit) AO Raiffeisenbank's assets," RBI said in a statement.

RBI said its Russian unit would appeal against the verdict "with suspensive effect" and RBI would take legal action in Austria "to mitigate damages by seeking enforcement against Rasperia's assets in Austria".

Its Russian unit would book a provision that "would reflect the amount awarded to Rasperia by the Russian court today minus the expected proceeds from enforcement of legal recourse against Rasperia's assets in Austria," RBI said.

($1 = 0.9628 euros)

(Reporting by Moscow bureau, Alexander Marrow in London, Francois Murphy in Vienna, John O'Donnell in Frankfurt and Gnaneshwar Rajan in Bengaluru; Editing by Tomasz Janowski and Diane Craft)