The United States and Australia have pledged to work together to develop, test and possibly operate a costly system to shoot down attacking ballistic missiles.

The two also agreed to conduct more U.S. military training exercises in Australia and to harmonize systems and procedures so their armed forces can fight together more efficiently.

U.S. President George W. Bush has made building a missile defense system a top priority, despite critics' questions about its cost and viability and the shift of the U.S. security focus to counterterrorism after the September 11, 2001, attacks.

Under a pact signed on Wednesday, the two nations laid the groundwork to jointly develop, test and possibly run such a system, with early work on advanced radar that can help detect ballistic missiles soon after launch, the Pentagon said.

Another early aim would be to equip a new Australian destroyer with missile defense capability, it added.

The initial U.S. missile defense system, costing more than $50 billion over the next five years, is designed to shoot down any inbound North Korean ballistic missiles that could be fitted with nuclear, chemical or biological warheads.

North Korea(DPRK) is seen as a major threat to U.S. allies in the Pacific because of its long-range missile and suspected nuclear weapons programs.

The Pentagon plans to broaden the system and to layer in interceptors based at sea, lasers aboard modified jumbo jets and possibly space-based rockets that could attack all three phases of an enemy missile's flight.

The United States will launch its effort this year by deploying a radar system and ground-based missiles in Alaska, designed to hit long-range missiles flying eastward across the Pacific.

Australian officials said they want to find ways to protect themselves, even though Australia faces no current threat from ballistic missiles.

"We have a responsibility to address not only the threats of today, but the threats that we might face in the future," Australian Defense Minister Robert Hill, who signed the pact with U.S. Defense Secretary Donald Rumsfeld, told reporters.

Australia will join South Korea, Japan, Britain, Germany, Israel, Italy, the Netherlands, Norway and Spain among countries working with the United States on missile defense, a U.S. official said.

Source: Agencies