ST. JOHN'S, N.L. - Aging tanks currently in Afghanistan and about to be replaced have proven their value, Defence Minister Gordon O'Connor said Wednesday, refuting criticism they should never have been deployed in the first place.

"Sending the tanks there was a really wise decision,'' he said. "They've really proved their worth. They have added immensely to the protection of our soldiers over there.''

Earlier this week, Gen. Andrew Leslie, Canada's top army officer, said he might have to pull the tanks out of service this summer because of the heat.

NDP defence critic Dawn Black said Tuesday it was "irresponsible'' to send the sweltering tanks to a country where temperatures can surpass 50 C.

A federal cabinet committee has approved the lease of 20 state-of-the-art tanks to replace the older armoured vehicles.

The recommendation, which is unlikely to be overturned, is now on Prime Minister Stephen Harper's desk for final approval.

O'Connor said a leasing agreement is still in the works. He acknowledged that the older tanks, which lack air conditioning, can get very hot inside for troops.

A Defence Department source said the cabinet priorities and planning committee approved the lease of the German-built Leopard A6M tanks last week.

The new tanks have air conditioning, as well as improved protection against road-side bombs and suicide vehicles, both of which have been packing progressively bigger punches lately.<

The leasing deal, which apparently includes access to ample spare parts, also gives Canada the option to purchase an unspecified number of additional tanks at a later date.

Currently, the army has 17 of its old 45-tonne tanks patrolling the desert and dirt roadways of rural Kandahar.