French President Nicolas Sarkozy will decide next month whether France should acquire a second aircraft carrier, bearing in mind the project's significant cost, Sarkozy's chief of staff said on Tuesday.

Sarkozy said during the campaign for last year's presidential election he would press ahead with the plan to build the aircraft carrier, a project under which France and Britain would jointly commission vessels to keep costs down.

But talks with Britain dragged on and Sarkozy has pushed back his decision on whether to give the project the go-ahead by several months.

"It is a subject on which the president will decide in mid-June," Sarkozy's chief of staff, Claude Gueant, told RTL radio.

That is when Sarkozy is due to formally approve a white paper stating France's defence priorities for the years ahead.

French officials have, however, been increasingly cautious in their public statements about the plan for a new aircraft carrier to supplement the Charles de Gaulle, which is undergoing maintenance work.

Defence Minister Herve Morin said last month budgetary constraints meant it would be difficult for France to afford the project, which he said would cost around 3.5 billion euros ($5.4 billion).

Sarkozy is seeking to keep public spending in check as he tries to reduce France's public deficit from a bigger-than-expected 2.7 percent last year to zero by 2012.

"A second aircraft carrier would be useful. Given its cost, the equipment priorities have to be set. It will be up to the president to do so. He will do so in a month," Gueant said.