WASHINGTON, June 20: The Pentagon has activated its new ground-based interceptor missile defence system following a North Korean threat to test a long-range missile, US media reported on Tuesday.

US officials said on Monday that any long-range missile launch by North Korea would be considered a “provocative act.” US intelligence satellites monitoring N. Korean missile sites reported this week that North Korea’s preparations have advanced to the point where a launch could take place within several days to a month.

Two US Navy Aegis warships are patrolling near North Korea as part of the global missile defence and would be among the first sensors that would trigger the use of interceptor missile, the Washington Times reported on Tuesday.

The US missile defence system includes 11 long-range interceptor missiles, including nine deployed at Fort Greeley, Alaska, and two at Vandenberg Air Force Base, California. The system was switched from test to operational mode within the past two weeks, the report said.

One senior Bush administration official told the newspaper that an option being considered would be to shoot down the Taepodong missile with responding interceptors.

Secretary of State Condoleezza Rice added that any launch would be a serious matter and “would be taken with utmost seriousness and indeed a provocative act.”

White House spokesman Tony Snow told reporters in Washington that President Bush had telephoned more than a dozen heads of state regarding North Korea’s launch preparations. He did not identify the leaders.

Pentagon spokesman Bryan Whitman said the US has made it clear to North Korea that the communist regime should abide by the missile-test ban it imposed in 1999 and reaffirmed in a pact with Japan in 2002.

“US Northern Command continues to monitor the situation, and we are prepared to defend the country in any way necessary,” said spokesman Michael Kucharek.

Any decision to shoot down a missile would be made at the highest command levels, which includes the president, secretary of defence and chairman of the Joint Chiefs of Staff.

John R. Bolton, the US ambassador to the United Nations, said earlier that the Bush administration is consulting other Security Council members on how to respond to a Taepodong launch.

US intelligence officials told reporters there are signs that the North Koreans recently began fuelling the Taepodong with highly corrosive rocket fuel. Normally, when liquid fuel is loaded into missiles the missile must be fired within five to 10 days, or it must be de-fuelled and the motors cleaned, a difficult and hazardous process.

The Taepodong was first tested in August 1998, and North Korea claimed that it was a space launch vehicle that orbited a satellite.