Citigroup received a $25 billion injection from the U.S. government in October as part of the $700 billion financial bailout that was aimed at thawing the credit markets, but concerns have emerged about how the money has been used.

Levin, who heads a Senate subcommittee on investigations, said he wanted to see whether the agreement included any commitments to help borrowers stay in their homes despite having trouble paying their mortgages.

"It's a simple request they so far have stiffed us," Levin, a Michigan Democrat, told reporters before closed-door meetings with incoming Obama administration officials on the financial bailout and an economic stimulus package.

"They promised us repeatedly we'd get the document so I intend to issue a subpoena this week to get that," he said, adding that he wanted to see it before determining whether to vote to release the second $350 billion of the bailout money.

President-elect Barack Obama's aides have been in discussions with the White House over whether President George W. Bush should ask Congress for permission to use the remaining $350 billion of the funds, which are aimed at stabilizing the financial system.

A Treasury spokeswoman said the loan agreement Citigroup signed for the $25 billion was identical to the language posted on the department's website.

Levin questioned whether Citigroup was "going to use it to keep people in their homes, to revise mortgages ... Are they going to use this to pay dividends to stockholders, which they shouldn't?"

"How are they going to handle executive compensation ... What are they going to do about the money being used to buy other banks?" he said.

Levin said he has also requested Treasury's agreement with the troubled insurer American International Group Inc but was unsure whether the department had said it would give the panel a copy.

In November, the Treasury Department agreed to invest another $20 billion in Citigroup preferred stock and help guarantee up to $306 billion in risky assets.

(Reporting by Jeremy Pelofsky, editing by Bernard Orr)