WASHINGTON - The Senate on Tuesday failed to ratify an international treaty intended to protect the rights of those with disabilities, as a bloc of conservatives opposed the treaty believing it could interfere with U.S. law.

The Senate voted 61-38 to ratify the Convention on the Rights of Persons With Disabilities, a tally that fell short of the two-thirds needed to sign on to an international treaty. All Philadelphia-area senators voted in favor except Sen. Pat Toomey (R., Pa.)

The 2006 treaty, which forbids discrimination of the disabled, has enjoyed bipartisan support. Sen. John Kerry (D., Mass.), chairman of the Senate Foreign Relations Committee, said the treaty would encourage other nations to develop the kind of protections the United States adopted 22 years ago with the Americans With Disabilities Act. The international treaty's thrust, he said, was a message: "Be more like us."

But the treaty has split Republicans. Among its most vocal supporters were Republican war veterans, including former President George H.W. Bush and former Sen. Bob Dole, who was wounded in World War II and made a rare return to the Senate floor Tuesday to observe the vote and lend his stature.

Other conservatives were deeply suspicious of the United Nations, which would oversee treaty obligations. Those who opposed the treaty included former Pennsylvania senator and Republican presidential candidate Rick Santorum, the father of a developmentally disabled child who had traveled to Capitol Hill last week to encourage fellow Republicans to vote no.

He and other conservatives argued that the treaty could relinquish U.S. sovereignty to a U.N. committee charged with overseeing a ban on discrimination and determining how the disabled, including children, should be treated. They particularly worried that the committee could violate the rights of parents who choose to home-school their disabled children.

"This is a direct assault on us," Santorum said.

Nations that have signed on to the treaty include China, Iran, and Syria. Opponents said that American approval might give the impression that the United States accepts how those nations treat their disabled citizens.

"The hard reality is that there are nation-states, like China, who do like to sign up to these organizations and gain the reputation for doing good things while, in fact, not doing good things," said Sen. Jon Kyl (R., Ariz.).

Supporters dismissed those fears as paranoid, noting that the treaty would change nothing in U.S. law without further approval from Congress.