US Democratic Senate Majority Leader Harry Reid, fighting a tough re-election battle, said a mosque should not be built near the site of the September 11, 2001 terrorist strikes in New York.
The US Constitution's "First Amendment protects freedom of religion. Senator Reid respects that but thinks that the mosque should be built someplace else," said the Nevada lawmaker's spokesman, Jim Manley.
Republicans including former vice presidential hopeful Sarah Palin and some other potential 2012 White House hopefuls have sharply assailed plans to build an Islamic center, including a mosque, two city blocks away from the site of the former World Trade Center.
Manley questioned whether Republicans were "being sincere," noting their ranks in Congress blocked a bill to help emergency workers who responded to the attacks in 2001 and now suffer serious, related health problems.
"If the Republicans are being sincere, they would help us pass this long overdue bill to help the first responders whose health and livelihoods have been devastated because of their bravery on 9-11, rather than continuing to block this much-needed legislation," he said in a statement.
The spokesman's comments came after Reid's Republican opponent in the November mid-term elections, Sharron Angle, had condemned the planned construction and challenged Reid to publicly state his position.
Republicans have denounced the planned construction on grounds that building a Muslim place of worship near the place where Islamist extremists attacked the United States is offensive to the victims of 9-11.
And they have served notice that they plan to challenge Democrats on the issue in the run up to the November elections that will decide control of the US Congress.
US President Barack Obama on Friday said he understood the emotions tied to the issue but made a passionate appeal rooted in an "unshakeable" belief in the freedom of religion asserted in the first amendment of the US constitution.
"I believe that Muslims have the same right to practise their religion as everyone else in this country. And that includes the right to build a place of worship and a community center on private property in Lower Manhattan, in accordance with local laws and ordinances," he said.
A day later, Obama clarified that he was not commenting on "the wisdom of making the decision to put a mosque there," a location he acknowledged as "hallowed ground," but on the rights at stake.