Jordan opposes it, as it wonders who will care for the hundreds of thousands of Palestinian refugees within its borders if the definition changes.

Whatever step the Obama administration takes in an election year is certain to resonate as Republicans and GOP presidential candidate Mitt Romney persist in questioning the president's commitment to Israel.

Ignoring administration objections, the Senate Appropriations Committee voted last Thursday to ask the secretary of state to report to the panel within a year on the number of people who have received assistance from the U.N. Relief and Works Agency for Palestine Refugees, and "whose place of residence was Palestine between June 1946 and May 1948 and who were displaced as a result of the 1948 Arab-Israeli conflict; and who are descendants."

The provision was a modified version of an amendment sponsored by Sen. Mark Kirk, R-Ill. It centers on the contentious issue of who is a Palestinian refugee -- just those were displaced 64 years ago by the 1948 fighting, or their descendants as well -- and their "right of return" to where they left.

The U.N. agency defines a Palestine refugee as any individual whose "normal place of residence was Palestine during the period 1 June 1946 to 15 May 1948 and who lost both home and means of livelihood as a result of the 1948 conflict."

Refugees also are any descendants of fathers who meet that definition.

The U.N. agency counted 860,000 individuals in 1951. Those registered refugees and their descendants now total 5 million living in Lebanon, Syria, Jordan, Gaza and the West Bank. Those who favor a distinction between the two argue that more than a half-century later, there are only 30,000 original refugees left.

The U.N. agency, which was established in 1949, provides health services, education and other assistance to these refugees, including 1.4 million spread out at 58 camps. Funds come from the United States, the largest donor with contributions of about $250 million a year, and other countries such as Britain, Norway and Sweden.

Since 1949, the United States has supported the U.N. agency at a cost of about $4.4 billion. The agency also has assisted refugees displaced by the 1967 Six-Day War.

For years, Israel was content with the U.N. agency caring for the refugees and steered clear of congressional efforts to cut funds for the organization, said Jonathan Schanzer, vice president for research at the Foundation for Defense of Democracies.

"Their concern is if UNRWA didn't exist, then they would be left holding the bag and would be required to provide services to millions of destitute Palestinians," Schanzer said in an interview.