Faced with growing international pressure, the Pentagon is changing its policy on cluster bombs and plans to reduce the danger of unexploded munitions in the deadly explosives.

The policy shift, which is outlined in a three-page memo signed by Defense Secretary Robert Gates, would require that after 2018, more than 99 percent of the bomblets in a cluster bomb must detonate.

Limiting the amount of live munitions left on the battlefield would lessen the danger to innocent civilians who have been killed or severely injured when they accidentally detonate the bombs.

Also, by next June the Defense Department will begin to reduce its inventory of cluster bombs that do not meet the new safety requirements.

The new Defense Department plan comes more than a month after 111 nations, including many of America's key NATO partners, adopted a treaty outlawing all current designs of cluster munitions. The agreement also required that stockpiles be destroyed within eight years.

Opponents have complained that the Pentagon has moved too slowly to reduce the cluster munitions from its inventory.

Cluster bombs scatter hundreds of smaller explosives over a large area, where those bomblets can sit for years until they are disturbed and explode.

U.S. leaders boycotted the May talks, as did Russia, China, Israel, India and Pakistan, all leading cluster bomb makers who cite the military value of the deadly explosives.

At the time, Cmdr. Bob Mehal, a Pentagon spokesman, said the elimination of cluster bombs from the U.S. stockpile "would put the lives of our soldiers and those of our coalition partners at risk."

Sen. Patrick Leahy, D-Vt., who has led efforts to outlaw cluster munitions, said the Pentagon's move is a step back. A defense policy issued by then-Defense Secretary William Cohen in early 2001, Leahy said, called for a similar reduction in submunitions from the cluster bombs by 2005.

"Now the Bush administration's 'new' policy is to wait another 10 years," said Leahy, calling it "another squandered opportunity for U.S. leadership." He said that in wake of the international treaty agreement, the Pentagon's plan to wait another decade before requiring the 99 percent detonation rate cannot be justified.

The use of cluster bombs has seen opposition in Congress, which last year passed a one-year ban on U.S. exports of such munitions to other countries. It is expected that the ban, which received bipartisan support, will be extended again by Congress.

The new Pentagon policy appears to plan for a possible end to that ban. The memo states that until 2018, the Defense Department would seek to transfer cluster munitions that don't meet the new 1 percent failure rate to other foreign governments. Any transfer would require that the foreign government not use them after 2018, and the sale would have to be "consistent with U.S. law," according to the memo.

The policy defends the use of the cluster bombs as effective weapons that "provide distinct advantages against a range of targets and can result in less collateral damage" than other weapons.

And the memo concludes by saying that "blanket elimination of cluster munitions is unacceptable" and commanders will use them in accordance with the law and international agreements "in order to minimize their impact on civilian populations."

A June report by the Congressional Research Service questioned whether it is feasible to design a bomb that will indeed detonate to the planned level of more than 99 percent.

"While such a high level of performance might be achievable under controlled laboratory conditions," the report said, other uncontrollable circumstances, such as landing in soft ground or getting caught in a tree or vegetation, could result in more unexploded duds.

According to the congressional report, the U.S. dropped more than 1,200 cluster bombs — containing nearly 250,000 submunitions — in Afghanistan from 2001-2002. And the U.S. and British forces used about 13,000 of the bombs — with more than 1.8 million bomblets — during the first three weeks of combat in the Iraq war.

When the international treaty was adopted, backers predicted that the U.S. would never again use the weapons, and it left open the possibility that European allies could order U.S. bases within their borders to remove cluster bombs from their stocks.

International leaders expect to sign the treaty in December.