Simon Property Group Inc has been corresponding with bankrupt General Growth Properties Inc about revising its offer, sources close to the matter said on Tuesday.

Although no final offer has been made, Simon Chief Financial Officer Stephen Sterrett met on Monday with General Growth representatives, a source said. In addition, Simon, the largest U.S. mall owner, has responded to a letter sent by General Growth that sought more details on how it would fund a deal and if Simon would offer stock to General Growth's equity owners, the source said.

Our goal is to maximize value for all stakeholders and we have developed a sound process to enable us to achieve that goal, a General Growth spokesman said in an e-mailed statement Tuesday evening. The company declined to elaborate further.

A representative from Simon said he did not know about the discussions.

Simon has been working to line up a $6 billion credit line with JPMorgan Chase & Co to finance a bid, sources said. In addition, the deal could include two sovereign wealth funds, sources said.

A partnership with private equity group Blackstone Group LP may or may not materialize, one source said.

General Growth, the No. 2 U.S. mall owner, rejected Simon's initial bid of making all unsecured creditors whole -- including interest -- with cash. That plan would also give equity holders about $6 per share and spin off General Growth's residential real estate business to the shareholders. Simon valued that business at about $3 per share.

Meanwhile, General Growth has been working with Brookfield Asset Management and Fairholme Capital Management to emerge as a stand-alone company. That deal would include offering creditors cash or stock, while equity holders would receive stock worth about $15 a share.

The General Growth plan includes splitting the company into two. One company would hold General Growth's highly valued malls, while the other would hold mostly non-income-producing development property and underperforming shopping centers.

The potential new offer from Simon would use a structure similar to the split under the company's plan that would allow an apples-to-apples comparison, the second source said.

Simon also has indicated to General Growth that it would allow the bankrupt company to do due diligence on Simon to help it evaluate Simon's equity, that source said.

Simon and General Growth have been corresponding through their attorneys, a source said. Chief executives David Simon and Adam Metz, of General Growth, have spoken a couple of times, the source said.

A U.S. bankruptcy court judge has given General Growth until April 13 to present its plan to emerge from bankruptcy. After that, a competing bid would be much more costly because General Growth's plan includes issuing about 120 million warrants.

Simon has urged General Growth not to enter into deal protections through warrants as proposed under the rival bid, the second source said.

Shares of General Growth were at $15.27 in after-hours activity, up 1.1 percent from their close of $15.10 on the New York Stock Exchange. Simon shares were at $84.08, down 0.1 percent from their close of $84.18.

Both sources declined to be identified because the talks are not public.

The case is In re: General Growth Properties Inc, U.S. Bankruptcy Court, Southern District of New York, No. 08-13555

(Reporting by Ilaina Jonas and Paritosh Bansal; Editing by Phil Berlowitz)