Indonesian state oil firm PT Pertamina (PTM.YY) and PT Indika Energy (INDY.JK) may jointly bid for BP PLC's (BP) stake in the Onshore West Java oil and gas block, a Pertamina spokesman said Monday.

"We are calculating how large a share to take and (how large a share will be taken by) Indika, as well as the issue of funding," Pertamina's vice president for communications, Basuki Trikora Putra, told reporters.

BP owns 46% of Onshore West Java, according to data from official oil and gas regulator BPMigas.

Tenders for the stake are scheduled for later this year.

BPMigas data estimates Onshore West Java will produce 135 million British thermal units of liquefied natural gas next year.

The regulator has previously said the block will produce about 28,000 barrels of crude a day this year, with output likely to fall to around 26,000 barrels a day in 2010.

BP's stake in the block is estimated to be worth around $600 million.

-By Deden Sudrajat, contributing to Dow Jones Newswires; 62 21 3983 1277; Reuben.Carder@dowjones.com