The so-called Hypersonic Cruise Vehicle, which would be designed to hit targets about 9,000 miles away, should be available by about 2025. Hypersonic means traveling at more than five times the speed of sound.

The goal is to demonstrate a system that could carry out prompt ``global reach missions'' without using overseas bases, the Defense Advanced Research Projects Agency, the Pentagon's cradle of new technologies, said in a notice released quietly two weeks ago.

``DARPA and the Air Force share a vision of a new transformational capability that would provide a means of delivering a substantial payload from the continental United States to anywhere on Earth in less than two hours,'' the notice said.

``This capability would free the U.S. military from reliance on forward basing to enable it to react promptly and decisively to destabilizing or threatening actions by hostile countries and terrorist organizations,'' said DARPA, which is jointly sponsoring the project with the U.S. Air Force.

Some of the system's building blocks should make it possible to launch a ``prompt global strike'' from the continental United States as early as about 2010 using rocket boosters, the draft notice said.

The program envisions a reusable, remotely piloted craft that could take off from a regular runway with 12,000 pounds (5,443 kg) of bombs and missiles or a new, rocket-assisted means of delivering such munitions, a draft overview said.

The project is called FALCON, short for Force Application and Launch from CONUS, or the 48 states, excluding Alaska and Hawaii, that make up the continental United States.

Jan Walker, a DARPA spokeswoman, described the effort as ``technology development and demonstration,'' as opposed to a plan to build, buy or deploy such a capability. Any such acquisition plans ultimately hinge on the U.S. Congress's power of the purse.

The draft notice cited U.S. military operations in Bosnia, Afghanistan and Iraq. ``While advancements in target identification and precision strike have been abundantly demonstrated, deficiencies in engaging and defeating time-critical and high-value, hard and deeply buried targets have also been revealed,'' it said.

The overview said the United States may find it increasingly difficult to use overseas bases to react quickly to perceived threats.

DARPA and the Air Force will host a so-called ``Industry Day'' on July 8 in Arlington, Virginia, to give contractors interested in the project the big picture, a notice on DARPA's Web site said.

Over the next 25 years, the new technology would free the US from dependence on forward bases and the cooperation of regional allies, part of the drive towards self-sufficiency spurred by the difficulties of gaining international cooperation for the invasion of Iraq.

The new weapons are being developed under a programme codenamed Falcon (Force Application and Launch from the Continental US).

A US defence website earlier this month invited bids from contractors to develop the technology and the current edition of Jane's Defence Weekly reports that the first flight tests are scheduled to take place within three years.

According to the website run by the Defence Advanced Research Projects Agency (Darpa) the programme is aimed at fulfilling "the government's vision of an ultimate prompt global reach capability (circa 2025 and beyond)".

The Falcon technology would "free the US military from reliance on forward basing to enable it to react promptly and decisively to destabilising or threatening actions by hostile countries and terrorist organisations", according to the Darpa invitation for bids.
                                                                     
The ultimate goal would be a "reusable hypersonic cruise vehicle (HCV) ... capable of taking off from a conventional military runway and striking targets 9,000 nautical miles distant in less than two hours".

The unmanned HCV would carry a payload of up to 12,000 lbs and could ultimately fly at speeds of up to 10 times the speed of sound, according to Daniel Goure, a military analyst at the Lexington Institute in Washington.

Propelling a warhead of that size at those speeds poses serious technological challenges and Darpa estimates it will take more than 20 years to develop.

Over the next seven years, meanwhile, the US air force and Darpa will develop a cheaper "global reach" weapons system relying on expendable rocket boosters, known as small launch vehicles (SLV) that would take a warhead into space and drop it over its target.

In US defence jargon, the warhead is known as a Common Aero Vehicle (Cav), an unpowered bomb which would be guided on to its target as it plummeted to earth at high and accelerating velocity.

The Cav could carry 1,000 lbs of explosives but at those speeds explosives may not be necessary. A simple titanium rod would be able to penetrate 70 feet of solid rock and the shock wave would have enormous destructive force. It could be used against deeply buried bunkers, the sort of target the air force is looking for new ways to attack.

Jane's Defence Weekly reported that the first Cav flight demonstration is provisionally scheduled by mid-2006, and the first SLV flight exercise would take place the next year. A test of the two systems combined would be carried out by late 2007.

A prototype demonstrating HCV technology would be tested in 2009.

SLV rockets will also give the air force a cheap and flexible means to launch military satellites at short notice, within weeks, days or even hours of a crisis developing.

The SLV-Cav combination, according to the Darpa document, "will provide a near-term (approximately 2010) operational capability for prompt global strike from Consus (the continental US) while also enabling future development of a reusable HCV for the far-term (approximately 2025)". The range of this weapon is unclear.