The Bush administration is banning land mines that cannot be located with metal detectors, a move designed to set an example to other nations and to protect mine hunters.

"We hope to inspire other countries to follow," said Lincoln P. Bloomfield Jr., assistant Secretary of State for political-military affairs.

Bloomfield said in an interview Tuesday that he did not think U.S. land mines (search) were causing any harm and that the only ones remaining were from the 1960s.

Last Feburary, the Bush administration said it intends to stop using land mines that are not timed to self-destruct to prevent harm to civilians.

However, the United States has declined to join the 150 nations that have signed an anti-land mine treaty (search), which bans all anti-personnel mines. The treaty permits land mines designed to destroy vehicles, including mines that are not detectable, officials said.

The Bush administration has gone farther by including land mines that are designed to hurt people and which do not self-destruct.

"De-miners must be able to clean out the battlefields," Bloomfield said in explaining the latest move. To be detectable mines must contain a certain level of iron content, he said.

"I don't think U.S. mines are really causing harm to the world, but we hope the example we are setting will be followed," he said.

Sen. Patrick V. Leahy, D-Vt., who far years has pressed for the outlawing of all land mines, called the move "a positive step, but a small one."

"No country, including ours, should continue using land mines, which indiscriminately kill or main thousands of innocent people every year, including our own troops," he said in a statement.