Senate Majority Leader Harry Reid has broken step with President Barack Obama on plans to build a mosque near the site of the 9/11 terror attacks, saying he disagrees with its construction.
A spokesman for Mr Reid, a Democrat facing a close election race in Nevada, said the senator thought the mosque should be built "somewhere else".
The president has come under fire after defending the planned mosque last week.
Many conservatives say Mr Obama is out of touch with the views of Americans.
Mr Reid's remarks came as campaigning for November's mid-term polls heats up.
Spokesman Jim Manley said in a statement that the senator respected that "the First Amendment protects freedom of religion", but still thought the mosque, planned for a site about two blocks away from the former World Trade Center, should be built in a different location.
Republicans have also threatened to use the mosque as a campaign issue this autumn.
A spokesman for Mr Reid's opponent in Nevada's Senate race in November, Sharron Angle, also spoke out against the president's defence of the mosque, saying Mr Obama "ignored the wishes of the American people, this time at the expense of victims of 9/11 and their families".
Spokesman Jarrod Agen said that families affected by the attacks on the World Trade Center considered the proposed mosque an "affront to the memories of their loved ones".
'Out of step'
Mr Obama told a White House gathering on Friday that the developers of the 13-storey Islamic community centre and mosque had a right to build it only blocks from Ground Zero in New York.
Republicans said Mr Obama was out of step with the country on the project.
"It's unwise to build a mosque at the site where 3,000 Americans lost their lives as a result of a terrorist attack," Senator John Cornyn said.
On Saturday, Mr Obama said he was backing the rights of the developers, not the "wisdom" of the project.
At a White House dinner on Friday celebrating Ramadan, the Muslim holy month, Mr Obama vigorously defended the developers' right to put the mosque there "in accordance with local laws and ordinances".
Muslims "have the same right to practice their religion as anyone else in this country", the president said.
But on Saturday Mr Obama clarified his comments, saying: "I was not commenting, and I will not comment on, the wisdom of making a decision to put a mosque there."
Nevertheless, a number of opposition Republicans hit out at the president's stance on the US Sunday talk shows.
The White House and the president's supporters have sought to frame Mr Obama's comments as a matter of conscience, not poll numbers, and argue that Republicans are inappropriately politicising the issue.
"This wouldn't be a controversy if it was a proposal to build a synagogue or a church," Democratic party chairman Tim Kaine said on CBS. "We don't prefer people and we don't punish people based on their religion."
While polling suggests a majority of Americans oppose plans to build the mosque, a Fox News poll released on Friday suggested 61% supported the developer's right to build the mosque.