WASHINGTON, April 27 (Xinhuanet) -- US Defense Secretary Donald Rumsfeld on Wednesday asked the Congress to fund research on nuclear bomb aimed at military targets hidden in underground fortified bunkers.

    "It seems to me studying it makes all the sense in the world," said Rumsfeld at a Senate appropriations subcommittee.

    Pentagon has said potential enemies are increasingly using underground fortified bunkers to protect key military assets from aerial bombing. Rumsfeld said the United States has no weapons capable to destroy them, and that more than 70 countries are pursuing these facilities.

    Opponents note that deadly radiative fallout from detonating such a "bunker buster" nuclear bomb cannot be prevented, and that even studying the possibility of making such a weapon encourages anuclear arms race.

    The Bush administration failed to get the research budget of 8.5 million US dollars from Congress last year. It is seeking the money in fiscal 2006, in addition to 14 million dollars for completing the study in 2007. Enditem