WASHINGTON (AP) - Four months before formally opening its doors, the new federal watchdog for policing mortgages, credit cards and other financial products is under attack from Republicans and banks.

Elizabeth Warren, the Harvard law professor who championed the Consumer Financial Protection Bureau and is now in charge of setting it up, faces the hostile fire directly on Wednesday. Republicans running the House Financial Services Committee will press her to answer their concerns - shared by banks and other business interests - that the agency and its director will have unfettered power over financial products used by millions of people and might abuse it.

"You have no guarantee what kind of hobby horses that person may ride, how out of control they might be," said Wayne Abernathy, an executive vice president of the American Bankers Association.

President Barack Obama has yet to nominate a director for the agency. Warren would have difficulty winning Senate confirmation because of Republican opposition. However, Obama could bypass that by using a recess appointment when Congress isn't in session to give her the job through 2012.

GOP lawmakers want the new agency's budget placed under Congress' control so lawmakers could threaten its financing if its actions displease them.

Republicans also want to dilute the bureau's power by moving decision-making authority from a single director to a bipartisan, multi-member commission. Rep. Spencer Bachus, R-Ala., chairman of the House Financial Services Committee, was preparing to introduce a bill with Rep. Shelley Moore Capito, R-W.Va., that would replace the director with a five-person commission with members from both political parties, according to a document obtained by The Associated Press.

In testimony prepared for her committee appearance, Warren is defending the bureau.

"If Congress is unhappy with a rule, it can overturn that rule," she said. She also said the courts could block the agency's actions and noted that the bureau is required to report frequently to Congress.

Democrats and their allies say they purposely gave the bureau clout and independence. Its creation was a marquee achievement of last year's financial markets overhaul law, which Obama and Democrats in Congress enacted last summer over GOP opposition.

The law "deliberately created an agency that was less likely to be manipulated by special interests," said Travis Plunkett, legislative director of the Consumer Federation of America. "That's the whole point."

The agency formally begins its work July 21 and cannot issue regulations until then.

"The economy collapsed because we didn't have any cops on the financial beat," said Edmund Mierzwinski, a program director for the consumer group U.S. PIRG. "Now they're trying to knee-cap the new cops before they even get started."

The chamber has been a leader in efforts to force changes in the bureau, arguing that it isn't accountable enough and might issue regulations that would hinder consumer and business access to credit.

Republicans and business allies also complain the new financial overhaul law is too vague and open to interpretation regarding the power it gives the bureau to protect consumers against "unfair, deceptive, or abusive acts and practices."

These provisions make the bureau "perhaps the single most powerful agency ever created by an act of Congress," Bachus said last week.

"It's a phony argument," Rep. Barney Frank said last week. "They don't like an independent consumer agency."

The GOP demands for changing the eight-month-old law have little chance of enactment with Obama in the White House.

Warren herself has come under attack from Republicans who say she has overreached. They have especially bridled at reports that she has been an adviser to federal agencies and state attorneys general trying to force big U.S. banks to change the way they modify mortgages and handle foreclosures. Last week, Sen. Richard Shelby of Alabama, top Republican on the Senate Banking Committee, called the legal effort "nothing less than a regulatory shakedown" by the bureau and other federal agencies.