WASHINGTON, Feb 21: Pakistan is expected to take up with the US administration the expected sale of Patriot missile defence system to India, diplomatic sources told Dawn on Monday.

A US defence team began briefing Indian officials in New Delhi on Monday on the Patriot missiles. In Washington's diplomatic circles the visit is seen as a prelude to the sale of the advanced anti-ballistic missiles to India.

"It's a serious development and comes into conflict with the existing nuclear deterrence in the Subcontinent," said a South Asian defence expert familiar with the system.

Since the May 1998, when both India and Pakistan tested their nuclear devices, there existed an undeclared balance of power in the Subcontinent based on the fear that a clash between the two nuclear-armed neighbours could lead to the destruction of both. But the Patriots, which could bring down an incoming missile, could seriously tip the balance in India's favour, making Pakistan vulnerable.

"If the Patriots are delivered to India, it will seriously imbalance Pakistan's strategic capabilities and can trigger an arms race in the Subcontinent," said the South Asian defence expert.

"The Pakistanis will need to do some soul searching to determine what effect it will have on their strategic defence," said the expert. When asked what Pakistan could do to meet the threat posed by the expected sale of Patriot missiles to India, the expert said: "Pakistan will have to acquire counter-capability. This new development will tip the balance in India's favour unless it is redressed."

"They will take up the issue with the Americans," said the expert when asked what could be Pakistan's immediate response. Sources in Washington said that the Bush administration gave clearance for a classified technical presentation of the system to India as part of the 'Next Step in Strategic Partnership' agreement initiated by the two countries last year.

The sources said the decision to give a 'classified briefing' about the Patriot system to India was taken during the first phase of NSSP that concluded in October. The NSSP envisages cooperation in what is known as the 'quartet issues' - civilian space and civilian nuclear fields, hi-tech trade and missile defence.

The conclusion of the first phase of the NSSP was marked by the US partially easing export controls on supply of equipment and technology for India's space and nuclear programmes. The Patriot is a long-range, all altitude and all weather air defence system to counter tactical ballistic missiles, cruise missiles and advanced aircraft.

The missile's range is 70km and it can climb to an altitude greater than 24 km. The minimum flight time - time needed to arm a missile - is less than three seconds and maximum flight time - time needed to reach a target - is just three-and-half minutes. India will be the sixth country with which Washington has shared this technology after Israel, Japan, Germany, Saudi Arabia and Taiwan.