HALIFAX - If upgrades to the air force's Aurora maritime patrol planes are stalled it could hurt the military's surveillance capabilities, the Liberal party's defence critic argued Monday.

In reaffirming the Liberals' position that there's plenty of life left in the nearly 30-year-old planes, Denis Coderre said surveillance on the East and West coasts, as well as in the Arctic, could be at risk.

"Those planes have a capacity to be perfect up to 2025,'' Coderre told a news conference, where he was joined by Nova Scotia MPs Geoff Regan, Scott Brison and Michael Savage.

"If we are replacing them ... and we're stalling those other (upgrades), you will have kind of a gap in some years when Canada won't be able to fulfil its own military duty. That's a problem in itself.''

The upgrades, started under the previous Liberal government, were put on hold in September on the Auroras, which are used also used to track submarines.

Defence Minister Peter MacKay was not available for comment, but defence sources have argued the air force could have new planes by the time the Aurora refit is completed in the 2012-13 time frame.

MacKay, who represents Nova Scotia in cabinet, said last month that the government is looking at the option of replacing the 18 Auroras, 14 of which are based in Greenwood, N.S.

An announcement on the aircraft's future is expected Dec. 18, almost one month after an earlier government deadline.

"We're asking the minister of defence to come clean to Nova Scotians and make sure that the future of the Auroras is sustained,'' said Coderre.

Coderre also argued that Ottawa has already spent more than $900 million to upgrade the planes and cancelling the project would cheat taxpayers. In 2005, the Liberals awarded two contracts totalling $961 million to Nova Scotia-based IMP Aerospace and L-3 Electronic Systems to upgrade the planes.

Some 2,000 jobs could be lost in Nova Scotia if the projects are called off, said Coderre.

Brison said the Liberals awarded the contracts because they provided the best value for taxpayers, security for the military and industrial benefits.

"Nothing has changed in terms of the benefits,'' said Brison, the party's industry critic.

"If in fact this decision is good for the taxpayer, or good for the region, or good for the Canadian Armed Forces, why doesn't the minister make the announcement now?''

The first two phases of the refurbishment upgraded the navigation, global positioning and radar systems of the aircraft.

The next two stages would improve the planes' data management system, sensors such as imaging radar, and offer protection against surface-to-air missiles.

The air force is reportedly looking at two potential replacement aircraft: Boeing's P-8 Poseidon, and the Astor, made by Bombardier.