UPDATE 1-White House sees momentum on financial reform

* Obama won’t accept weakened regulations

* White House official: bill must tackle “too big to fail”

* Obama to meet with top Democrats, Republicans (New throughout with more details)

WASHINGTON, April 13 (Reuters) - The White House said on Tuesday momentum was building for the effort to rewrite U.S. financial regulations and urged Republicans to join the push.

A day before President Barack Obama was to sit down with top Democratic and Republican lawmakers to discuss legislation on financial reform, a White House official said Obama will not allow a “race to the bottom” on regulations.

“We believe momentum is on the side of greater accountability for Wall Street and strong protections for consumers and we hope Republicans in Congress will join us in a constructive conversation about how to move a strong bill forward,” White House spokesman Amy Brundage said in a statement.

“This is not a race to the bottom and the president will not accept attempts to weaken provisions in the bill or carve loopholes,” she said.

Brundage said the White House wants to ensure the bill “has real authority” to tackle the problem of “too big to fail” financial institutions.

Senate Republican Leader Mitch McConnell, who will be among those in the meeting with Obama on Wednesday, spoke out strongly against the Democratic version of the bill.

The sweeping regulatory reform measure would impose tougher rules on banks and capital markets in response to the worst financial crisis since the Great Depression. It would also bolster protections for consumers of financial products.

Now that he has secured a victory on landmark healthcare reform legislation, Obama is pushing regulatory restructuring as his top domestic priority and hopes for a final Senate vote on the measure within weeks. He will need at least some Republican support.

In addition to McConnell, House Republican leader John Boehner will attend the meeting with Obama.

The Democrats in the meeting will include Senate Majority Leader Harry Reid, Speaker of the House of Representatives Nancy Pelosi and House Democratic leader Steny Hoyer. (Additional reporting by Alister Bull; Writing by Caren Bohan; Editing by Jackie Frank and Bill Trott)