"At a time when relations between India and Pakistan have thawed, it would be a pity that the supply of F-16 fighter planes would destroy the fragile environment in South Asia and give rise to an arms race in the region," Russian ambassador to India V. Truvinikov said in this north Indian hill station.

"America should think twice before the supply of these fighter planes to Pakistan."

The United States recently announced it was selling the sophisticated jets to Pakistan while making a similar offer to New Delhi.

India has so far not accepted the offer, saying that details of the deal need to be discussed first.

However, it has expressed concern over the decision to sell the jets to rival Pakistan, saying the weapons could be used against India.

India has been Russia's long-time ally and 70 percent of its military supplies come from Moscow.