The defense contractor building a fleet of new presidential helicopters has privately advised the Pentagon that its total cost has gone up by at least 1.8 billion dollars in the past year to 13 billion dollars.

The development makes the embattled program less likely to be completed, reports the Washington Post.

President Obama last month ordered a Pentagon review of the program, which was already under scrutiny because of last year''s estimate that the cost had risen from six billion dollars to 11.2 billion dollars.

The Navy passed along Lockheed Martin's new estimate to lawmakers, the officials said.

The extra expenses stem from delays and design changes that have added substantial weight to the helicopters, making them cost more than 460 million dollars a piece.

But several officials cautioned yesterday that the Pentagon''s review is likely to show that the eventual cost will be even greater than Lockheed has forecast.

Spokesmen for Lockheed and the Navy, which is overseeing the program, declined to comment. (ANI)