On Wednesday, JPMorgan Chase & Co Chief Executive Jamie Dimon will be left out in the cold.

The outspoken boss of the second-largest U.S. bank was one of the few major bank heads to fail to receive an invitation to the signing of the U.S. financial reform bill, a JPMorgan Chase spokeswoman said on Tuesday.

The most comprehensive U.S. financial regulatory overhaul in decades, the bill targets Wall Street risk taking and also aims to bolster consumer protections.

Dimon once enjoyed a close relationship with U.S. President Barack Obama. But Dimon emerged as a vocal critic of the administration's efforts to reform the U.S. banking industry, which culminated in the Dodd-Frank bill that passed the Senate last week.

There was no immediate comment from the White House.

Bank of America Corp CEO Brian Moynihan, Citigroup Inc's CEO Vikram Pandit, and Morgan Stanley's James Gorman all received invitations, people familiar with the matter said. Pandit is the only CEO scheduled to go, a person familiar with the matter said.

The banks themselves declined to comment.

Representatives for Goldman Sachs Group Inc, which last week agreed to pay U.S. regulators $550 million to settle a fraud lawsuit, did not respond to requests for comment.

Earlier on Tuesday, the White House said there would be about 400 people at the signing, including business leaders, Americans affected by the financial crisis and members of Congress.

White House spokeswoman Amy Brundage said invited guests included Robert Diamond, president of Barclays Plc, and Joseph Dear, chief investment officer of the California Public Employees' Retirement System.

(Reporting by Maria Aspan; Additional reporting by Elinor Comlay, Joe Rauch, Steve Eder, Dan Wilchins and Patricia Zengerle; Editing by Tim Dobbyn)