MANILA, March 1 - The Philippines' Metro Pacific Investments Corp (MPI.PS) has set up a unit with a sister firm that will become the biggest stakeholder in Manila Electric Co (MER.PS), enabling Metro to extend an option to buy more shares in the power firm.

The move gives Metro Pacific, a unit of Hong Kong's First Pacific Co Ltd (0142.HK), more time to secure funding to exercise a call option on a November deal to buy 6.6 percent of Meralco for 22.4 billion pesos ($486 million), Metro and its sister firm Pilipino Telephone Corp (PLTL.PS) said on Monday.

The two companies said in a statement they would transfer a 28.2 percent stake in Meralco to the new unit, Beacon Electric Asset Holdings Inc, which will become the largest shareholder in the country's biggest power utility.

The consolidation of the Metro Pacific and Piltel holdings in Meralco will also allow Beacon to access debt financing for any additional purchases of Meralco shares, using its Meralco shares as security, the companies said in a statement.

They said Beacon had until May 15 to exercise the option.

A syndicate of banks has offered a credit line of 18 billion pesos over 10 years to Beacon, Metro Pacific CEO Jose Maria Lim told analysts at a briefing.

Beacon will be equally owned by the two firms. Piltel, a unit of Philippine Long Distance Telephone Co (TEL.PS), is also partly owned by First Pacific.

Manuel Pangilinan, who is the chairman of PLDT, the country's most valuable listed firm, Metro Pacific and Piltel, will chair Beacon's five-member board.

Both Metro Pacific and Piltel consider their Meralco stakes as a strategic investment and their consolidation in Beacon allows them to strengthen their ownership and maximise returns over the long term, Pangilinan said.

The companies said First Pacific had agreed to subscribe to 6.6 billion pesos of Metro Pacific's three-year convertible bonds to partially fund its subscription of Beacon shares. ($1=46.115 pesos) (Reporting by Monicca Egoy; Editing by John Mair)