Petron Corporation disclosed to the stock exchange that it has a $550 million offer from a subsidiary of a London-based company to purchase the 40 percent stake of Aramco Overseas Company, a Saudi oil firm.

If the deal pushes through, it will mark the end of a 14-year relationship between Petron, the Philippines' largest oil refining and marketing firm, and Saudi Arabian companies.

The offer is to purchase 3,750,000,009 Petron shares for $0.15 per share or about P6.08 per share. It closed at P6.10 per share Thursday.

SEA Refinery Holdings, a company owned by Ashmore group, a global asset management company made the offer.

Ashmore, which manages $36.5 billion worth of assets, is listed in the London Stock Exchange.

Petron was a state-owned oil company until 1994, when Aramco and the Philippine government entered into an agreement to each own 40 percent of Petron Corp..

It then sold the remaining 20 percent to the public.

The entry of the Saudi firm then was supposed to ensure crude oil supply from the Middle East.

In a press statement, Petron Chairman and CEO Nicasio I. Alcantara said that, "regardless of the company's ownership structure…we will continue to focus on initiatives to sustain our growth momentum and deliver the best value to our stakeholders."

Alcantara boasted that Petron has "a dynamic and experienced management team, proven strategic initiatives to ensure growth, a strong commitment to good governance and solid operating performance."

Petron has a 40 percent market share of the country's total fuel requirements and has 1,250 service stations, the largest network in the country.