WASHINGTON (Reuters) - The majority of Americans favor giving millions of illegal immigrants a way to earn citizenship, according to a survey released on Thursday, highlighting public support for efforts in Congress to reform immigration law.

In the Public Religion Research Institute poll, 63 percent of Americans said they supported a path to citizenship for undocumented foreigners if they meet certain requirements.

Seventy-one percent of Democrats and 53 percent of Republicans backed eventually allowing illegal immigrants to become Americans.

The path to citizenship idea is the centerpiece of both a bipartisan immigration plan in the Senate and President Barack Obama's immigration reform proposals.

This week, Republican Senator Rand Paul, a libertarian and favorite of the conservative Tea Party movement, called for legalization of the 11 million undocumented foreigners, the majority of who are from Latin America.

He stopped short of specifically urging a path to citizenship but his statement nonetheless represents a shift in thinking for many conservatives, many of whom used to advocate deportation.

"In many ways, we are seeing the leaders in Congress catching up to where rank and file Republicans are on this issue," said Robert Jones, the CEO of the Public Religion Research Institute.

"Republicans, a couple of years ago, were holding the line against a path to citizenship... Now, there have been more Republican (lawmakers) talking about a middle option," he said.

Republicans have been forced to retool their message to non-white voters after Hispanics and other minority groups threw their support behind Obama in the November presidential election.

The poll found that fewer Americans thought that the best way to solve the country's immigration problems was to secure U.S. borders, and arrest and deport everyone living in the United States illegally. This year, 29 percent of those surveyed said that was the best policy, down from 36 percent in 2011.

The survey, conducted between March 6 and 10, was based on 4,465 Spanish and English telephone interviews with adults. The margin of error is plus or minus 1.7 percentage points.

The poll was conducted in partnership with the Brookings Institution think tank.