"While we support diplomatic efforts by your administration to prevent such a launch from occurring, we also believe prudent steps can be taken to make use of our missile defense capabilities should the United States or our allies be put at risk," they said in a message to Obama dated Tuesday.

Republican Representative John McHugh, the party's top member on the House Armed Services Committee, led the group of 16 House Republicans in expressing concerns about US plans for responding to the possible launch.

"Recent reports suggest that Japan has authorized its military to shoot down any debris from the North Korean rocket that might fall toward its territory," they said. "We respectfully encourage you to make a similar decision."

"We also ask for your response as to what plans and preparatory measures your administration is taking should the North Korean rocket endanger the United States or our allies," they wrote.

Pyongyang has said it will launch a communications satellite over northern Japan between April 4 and 8. The United States and its Asian allies suspect the launch is a cover for a long-range ballistic missile test.

Japan -- regarded as a pacifist state since its World War II surrender -- has deployed land- and sea-based anti-missile systems to try to intercept the rocket should it start falling toward Japanese territory.

The US lawmakers wrote Obama that the uncertainty about exactly what North Korea was preparing to launch was "deeply disturbing" and charged that a recent Iranian satellite launch showed Pyongyang was still spreading missile know-how overseas.

"Furthermore, any such launch would explicitly violate United Nations sanctions and pose a provocative and destabilizing threat to the region and the American people," they said in the letter.

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