State pension fund Government Service Insurance System (GSIS) delivered a surprise on Tuesday after almost quadrupling its stake in Manuel Pangilinan-led Metro Pacific Investment Corp. (MPIC) to nearly 12 percent days before the conclusion of the company's P55-billion privatization bid.

Shares of the infrastructure giant fell 1.2 percent to P5.10 apiece as investors weighed the implications to Metro Pacific's proposed delisting from the Philippine Stock Exchange due to its low stock market valuation.

GSIS' upsized stake, worth about P17.8 billion at the tender offer price of P5.20 per share, gives the pension fund enough boardroom sway to block the delisting plan. But several market observers said GSIS was likely strengthening its position to negotiate better buyout terms from the bidding consortium—comprised of Indonesian tycoon Anthoni Salim's First Pacific Group, the Ty family conglomerate GT Capital Holdings, Japan's Mitsui Group and Pangilinan, chair and CEO of Metro Pacific.

"Either they raise the price to a level that is acceptable to GSIS or they can no longer delist," COL Financial Group chief equity strategist April Lynn Tan told the Inquirer on Tuesday.

"GSIS, after all, doesn't need the liquidity given the nature of their funds. They can and should always think long term if and when they buy shares of stocks," she added.

GSIS officials did not immediately respond to a request for comment on Tuesday.

Several stockbrokers polled by the Inquirer said most of their retail investors decided to sell their shares after the Metro Pacific bidding consortium improved the offer by 12 percent to the "best and final" price of P5.20 per share.

The tender offer ends Sept. 7 but stockbrokers expect most documents filed by today. INQ