(Adds details on OMV business in Iran)

VIENNA, June 23 (Reuters) - Iran still owes Austrian energy firm OMVan unspecified but significant amount of money, which is slowing down deal talks there, the oil and gas group's Chief Executive Rainer Seele was quoted as saying by Austria's Trend magazine.

Last month OMV signed a memorandum of understanding with the National Iranian Oil Company with a view to reviving its activities in Iran.

"We are in interesting talks (in Iran). But first the financial conditions have to improve. This will not happen that fast - not least because we still have outstanding claims against Iran," Seele said in an interview with Trend released on Thursday ahead of publication on Friday.

He declined to give details. "It's not 2.50 euros ($2.85), otherwise the management would not take care of this. It pays off to tackle this."

An OMV spokesman also declined to give details.

Seele, who took the helm at Austria's biggest company last July, has targeted Iran, Russia and the United Arab Emirates as production sites in a push away from expensive North Sea field exploration.

The outline deal with Tehran covers several areas from oil and gas field evaluation to crude oil and petroleum product swaps.

Most international sanctions on Iran were lifted in January after Tehran reached a deal with world powers under which it agreed to shrink its nuclear programme, but some hurdles, especially with regard to financial transactions, remain.

OMV's envisaged projects are in the Zagros area in western Iran, including the Cheshmeh Khosh and Band-E-Karkheh fields where OMV had started operations in 2001, and the Fars field in the south. ($1 = 0.8780 euros)

(Reporting By Alexandra Schwarz-Goerlich; writing by Shadia Nasralla; editing by Kirsti Knolle and Francois Murphy) ((Shadia.Nasralla@thomsonreuters.com; +43 153 11 2256; +43 664 390 6505;))