The Pentagon is using sophisticated satellites that orbit Earth in a bid to track down its enemies and keep a round-the-clock watch on unfriendly foes.

The technological advantage can prove lethal, as witnessed by the recent air raid that killed the long-wanted Al-Qaeda in Iraq leader Abu Musab al-Zarqawi.

"Space capabilities have revolutionized the way we fight today by providing our forces with battlefield situational awareness, environmental understanding, precise weapons effects, and the ability to control and synchronize military operations on a global scale," Lieutenant General Robert Kehler, the deputy commander of US Strategic Command, told a Congressional panel.

Initially satellites had been fired into space to back surveillance and reconnaissance operations, but they are now being used more and more to back "war fighting operations in real time," Michael O'Hanlon, an expert at the Washington-based Brookings Institution, told the same panel at Wednesday's hearing.

Kehler highlighted the example of Zarqawi's death following a strike from "an on-called air delivered GPS guided weapon," referring to the US global positioning satellite (GPS) system.

Used by the Pentagon to give an accurate position on Earth in real time, 24-hours a day, the GPS system uses a group of 28 satellites orbiting the globe to pinpoint an exact position, and is also widely used commercially.

America's military satellites are also a crucial part of the US anti-missile defense system and its ongoing development, which has come into focus amid North Korea's reported plans to test a long-range missile.

The system is designed to detect a potential missile launch targeting the United States and to deploy a US interceptor missile to destroy any incoming missile attack from a foreign state.

The Defense Department (DOD) has also "steadily increased" its use of commercial satellites to support its military operations around the world, according to David Cavossa, the executive director of the Satellite Industries Association.

"DOD estimates that commercial satellite systems provided over 80 percent of the satellite bandwidth supporting Operation Iraqi Freedom," Cavossa said.

At present the US lead in defense satellite technology is dominant, with Russia failing to replace decommissioned satellites due to chronic military under funding, and China only starting to harbor its space ambitions, analysts said.

But this supremacy could still be threatened and even force the United States to develop anti-satellite missile to target those of its potential foes, they added.

"This moment of American predominance in space is highly desirable. Yet it cannot, and will not, last," O'Hanlon said.

"Our enemies clearly understand the reliance we place in our space capabilities," Kehler said. "We cannot assume that space will be a sanctuary for US national security assets and must take prudent steps to ensure that we have the capability to protect our space assets."

O'Hanlon said China posed the most serious potential space threat in space because it is both developing its own satellite program while also probing for "vulnerabilities" in the US system.

"China may be the most notable example of a country that is doing both," O'Hanlon said, while noting that Beijing's efforts so far have produced limited success and that the program was developing quite slowly.

But long-term military prognoses are difficult, and due to ardent opposition from countries like Russia, Washington may be forced to "militarize" space by creating anti-satellite missiles, analysts said.

"There is a real possibility that, at some future point, the United States may have powerful reasons to develop anti-satellite weapons itself," said O'Hanlon.

He noted that before Donald Rumsfeld became defense secretary, he chaired a space commission in which he warned of a "space Pearl Harbor" unless Washington took stronger steps to protect its future interests in the field.

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