* EU officials says date not yet fixed
* European Commission also seeking progress on gas talks (Adds EU official, context, detail on gas)
KIEV, Aug 19 (Reuters) - Ukrainian President Petro Poroshenko will visit to Brussels on Aug. 30 at the invitation of top European Union officials, the presidential website said on Tuesday.
A tug of war between the EU and Russia over Ukraine has embroiled the former Soviet republic in a crisis that worsened when Moscow annexed Ukraine's Crimea region in March.
Poroshenko confirmed he would accept the invitation in a telephone conversation with European Commission President Jose Manuel Barroso, the presidential website said.
A senior EU official, who asked not to be named, confirmed that Poroshenko had been invited to Brussels, but said the date had not been confirmed.
The official said Poroshenko was not invited to a summit of EU leaders taking place on Aug. 30 but would instead hold bilateral talks with Barroso and Herman Van Rompuy, president of the European Council.
Separately, the Commission said it was sending EU foreign policy chief Catherine Ashton and its trade and energy commissioners to talks in Belarus on Aug. 26, which will be attended by Poroshenko and Russian President Vladimir Putin.
Commission spokeswoman Marlene Holzner said on Tuesday that Energy Commissioner Guenther Oettinger would use the Minsk talks to seek further trilateral talks between the Commission, Ukraine and Russia with the aim of resolving the row between Kiev and Moscow over gas pricing.
The dispute has led Gazprom to cut off gas to Ukraine, raising the risk of knock-on disruption of EU supplies.
Oettinger will also hold bilateral talks on the same issue with Russian Energy Minister Alexander Novak on Aug. 29 in Moscow, Holzner said. (Reporting by Richard Balmforth in Kiev and Barbara Lewis in Brussels, Editing by Alison Williams)