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WASHINGTON (AFP) — The United States on Tuesday announced a review of its often-criticized terror alert system created in the wake of the September 11, 2001 attacks.

The system includes a color-coded public warnings, which range from green, symbolizing a low risk of attack to red, which points to a severe threat.

Homeland Security Secretary Janet Napolitano said in a statement a bipartisan panel of experts would report on the efficiency of the system within 60 days.

"My goal is simple: to have the most effective system in place to inform the American people about threats to our country," Napolitano said in a statement.

The secretary -- who heads a department also created after the attacks -- said she had appointed a senior George W. Bush security adviser Fran Townsend to lead the panel.

Critics say such threat coding is too vague and provide little or no actionable information for travelers, while causing alarm.

In 2003, a congressional report warned that levels were so vague that they would lead the public to question their usefulness.

But scrapping the system is likely to provide fodder for President Barack Obama's critics, who accuse him rolling back anti-terror polices to the detriment of national security.

Former vice president Dick Cheney has frequently spared with the Obama since leaving office, accusing him of making the country more vulnerable to attack.

The current threat level is yellow, "a significant risk of terrorist attacks," where it has stood since since 2004, although specific sector or route advisories have changed.

In August 2006, the threat level was raised from orange to red for flights to the United States from Britain, after authorities in London unraveled a plot to blow up as many as 10 trans-Atlantic airliners.

The threat level is published on the Department of Homeland Security's website and features in public service announcements in US airports.

Britain has a similar system, operated by the internal security service commonly known as MI5.

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