WASHINGTON  - Leaders of a wide variety of national organisations and Congress are putting pressure on U.S. President Barack Obama to reconsider his predecessor's policies of allowing the use, transfer and production of weapons that have been shown to indiscriminately maim and kill civilians.

In an open letter to Obama organised by the U.S. Campaign to Ban Landmines (USCBL), 67 heads of organisations, representing a cross-section of U.S. society from activists to doctors and religious groups, called for the administration to review the U.S. policy of noncompliance with treaties banning munitions that cause undue harm to civilians.

A cluster bomb in the yard of a house in the southern Lebanese village of Sultaniyeh (THOMAS COEX/AFP/Getty Images) "We write now to urge you to launch a thorough review within the next six months of past U.S. policy decisions to stand outside the treaty banning cluster munitions, as well as the treaty banning anti-personnel landmines," said the letter released Wednesday.

"Reconsidering these two treaties - and eliminating the threat that U.S. forces might use weapons that most of the world has condemned - would greatly aid effort to reassert our nation's moral leadership."

On Thursday, key members of the U.S. Congress introduced bipartisan legislation to ban the use of almost all cluster munitions. The Cluster Munitions Civilian Protection Act would ban all cluster munitions with a dud rate of greater than one percent.

Cluster munitions explode in midair, releasing dozens, sometimes hundreds of tiny bomblets. The scattered submunitions have been documented to cause many civilian casualties, even long after a conflict is ended.

Duds, or failed cluster bombs, leave behind unexploded ordinances that act as "de facto landmines that threaten civilians and local communities long after conflicts have subsided," according to a press release about the letter and Congressional legislation from the Friends Committee on National Legislation (FCNL).

The letter and the legislation should act in concert to show Obama that there is broad support for the ban, said Lora Lumpe, the legislative representative at FCNL, the group that houses USCBL.

"For [Obama] to sign both these treaties, the cluster bombs one in particular, it's going to take leadership," she told IPS. "He will have to know that there's support from the House and Senate because the Pentagon has expressed the desire to keep using these munitions."

Indeed, in June 2008, when momentum was gathering for a cluster bomb ban and over 100 nations had pledged to sign the treaty, the George W. Bush administration scrambled to justify its lack of support.

Pentagon chief Robert Gates, who has stayed on in the new administration, said that the "blanket elimination of cluster munitions was unacceptable" because the weapons have "clear military utility" and can "save U.S. lives".

But Lumpe told IPS that in terms of solely military utility, any weapon could be justified.

She also said the Department of Defence has pointed out that the treaty does not ban most of the cluster munitions used in the world, but that was something of a self-fulfilling prophecy.

"If the U.S. moved in it would ban more than half of the cluster munitions used in the world," she said. Furthermore, by signing on, the U.S. could put pressure on the other large-scale users of cluster bombs who have not complied with the treaty either, such as Russia and China.

"I'm confident that if there was a policy review that included the full range of U.S. interests at stake, they would see that there is no need to hold on to the threat of these munitions that most of the rest of the world has banned," FCNL's Lumpe told IPS.

In December 2008, 95 countries signed onto the Convention on Cluster Munitions in Oslo, Norway. With the often unilaterally-inclined Bush administration still in power, the U.S. was notably absent.

At the time, an Obama transition team spokeswoman said that the then-incoming administration would "carefully review the new treaty and work closely [with] our friends and allies to ensure that the United States is doing everything feasible to promote protection of civilians."

In addition to playing to Obama's transition team's comments and his "clear commitment to restoring U.S. Moral leadership," Wednesday's letter also gave a nod to the futility of using munitions that harm civilians in today's counter-insurgency conflicts, where support of local civilians is considered paramount.

"The use of weapons that disproportionately take the lives and limbs of civilians is wholly counterproductive in today's conflicts, where winning over the local population is essential to mission success," said the letter.

The U.S. is currently embroiled in two such wars in Afghanistan and Iraq, and, especially with regards to Afghanistan, Obama had spoken on the campaign trail about the need to mitigate civilian casualties.

Many of the U.S.'s closest allies signed the treaty, including parties as diverse as Britain and other European allies and the U.S.-formed government of Afghanistan.

The letter did note some U.S. progress in working against these munitions, such as Gates's policy memo last year that stipulated that the U.S. would stop using cluster bombs with dud rates greater than one percent in 2018, and U.S. efforts in demining operations around the world.

But it said "these contributions are undermined by U.S. nonparticipation in the decade-old Mine Ban Treaty and the new Convention on Cluster Munitions".

"These steps, while positive, are not nearly enough," it said.

The letter was copied to key members of Obama's cabinet, such as Gates, Secretary of State Hillary Clinton, National Security Adviser James Jones, and U.N. Ambassador Susan Rice. Seven members of Congress, including the current bill's lead sponsors, Sens. Patrick Leahy and Diane Feinstein, and Rep. Jim McGovern, were also copied.