NEW YORK (CNN/Money) - IDT Corp. unveiled more details of its bid for key WorldCom assets, saying it is proposing to pay $800 million in stock now and then have the rest of the payment come from the acquired operation's future cash flows.

IDT Chairman Howard Jonas said he believes his company, which has a history of buying distressed telecommunications assets, is the only company that is in a position to bid for the MCI consumer and small business long distance service, as well as its MFS Communications and Brooks Fiber units. Both companies are competitors of regional Bell telephone companies in providing local phone service to customers.

"There is nobody in a position now to make a more substantive offer on these WorldCom assets because frankly there's no guarantee of the integrity of the books," he said in a conference call with reporters. "If the books resemble the truth, this is a very good offer."

He said that the company had been shopping the MCI business to IDT for more than a year, but that their asking price was far above what IDT believed was reasonable in the market. He accused WorldCom's top executives of trying to hide from the offer because they want to keep control of the company, saying that WorldCom CEO John Sidgemore returned a call at 5 a.m. earlier this week, and has not been available since then.

"When these problems came up and we knew there were creditors who would be looking for top dollar, we decided to go public with the bid," he said.

MCI was not immediately available to comment on Jonas' comments. Earlier a spokeswoman had repeated a previous statement that, "WorldCom will consider any serious offer but it is highly unlikely we would consider selling any of our core assets such as MCI or local assets."

Shares of WorldCom (WCOME: up $0.03 to $0.25, Research, Estimates), the nation's No. 2 long distance provider and a major handler of Internet traffic, closed Friday trading up 3 cents, or 13.6 percent, to 25 cents. Shares of IDT (IDT: up $0.20 to $16.70, Research, Estimates) closed up 20 cents, or 1.2 percent, to $16.70. U.S. equities markets closed early Friday while Jonas was still talking with reporters.

Jonas said he believes IDT's offer would end up coming to $5 billion, based on his understanding of the cash flow of the businesses he's proposing to buy. But he said the offer could go higher or lower depending upon performance in the coming years.

He also said IDT would be interested in WorldCom's Enterprise business, but that he would have to get access to the books before making an offer. And he said that he's convinced that UUNet, the Internet backbone business that carries much of the traffic on the Internet, will fetch at least $7 billion, and attract bidders such as Microsoft Corp. (MSFT: Research, Estimates) and AOL Time Warner (AOL: Research, Estimates).

"No question we'd like to buy UUNet, but we're not Time Warner, we're not Microsoft. We can't afford that kind of price," he said.

News of IDT's interest in WorldCom's assets has helped lift WorldCom stock up from a low of 5 cents earlier this week. The stock was also helped by the fact that the threat of its stock being dropped from the Nasdaq exchange as early as Friday was halted by the company filing an appeal of the delisting order. A hearing on that matter will come sometime in the next 45 days, said Nasdaq spokesman Scott Peterson.

Jonas didn't hold out much hope for WorldCom shareholders.

"While I believe the stock is undervalued I'm not pushing it," he said. "Today is not a day to buy stock. Today is day to make sure the telephone works."

To that end he also offered guarantees to customers of the WorldCom businesses that he is seeking to buy, including offering phone cards for MCI long distance customers. He said that IDT offer of backup service will allow customers to stay with WorldCom until a purchase is completed. He said that WorldCom is seeing "massive" defection of customers, a charge that company spokesmen have denied.

Jonas said any deal needs to be completed quickly and that if the deal doesn't happen in six weeks, the value of WorldCom's MFS Communications business will be largely destroyed. He also plans to talk to federal officials next, specifically the Securities and Exchange Commission, about the company not responding properly to its offer.

He said he believes the board now owes a fiduciary duty to the company's bondholders, rather than its shareholders. He said that IDT would make some limited purchase of WorldCom notes in the coming days so that it has standing to bring lawsuits, but that it does not intend to try to get control of the company or its assets through widespread purchase of its bonds.

The Wall Street Journal reported Friday that the company is negotiating with bondholders to convert debt into equity as part of a pre-approved bankruptcy filing to help it emerge from its current financial crisis. A bankruptcy filing would likely wipe out current shareholders' stake in the company, the paper reported.

The Journal reported Friday that holders of $26 billion in WorldCom bonds are negotiating whether to accept equity for their debt as part of what would be the nation's largest bankruptcy case ever.

The company has a total of $32.8 billion in debt, the paper said. It reported that the bank debt does not have collateral, and bondholders are worried that as WorldCom seeks new bank financing the banks will try to negotiate collateral that gives them priority in repaying their debt.

"The company is clearly aware of the horribly visceral reaction from the bondholders if the company were to give preferential treatment to the banks," the paper quoted one person involved with the bondholders.

The paper said the day before the company disclosed its improper accounting practices, bonds that were coming due next year were trading at 79 cents on the dollar, then fell to 13 cents on the dollar a day later. The value of the bonds has recovered a few cents from those lows and could recover further if traders believe WorldCom has the resources to pay interest on bonds due July 15.

The Wall Street Journal also reported Friday that the Justice Department wants the company to suspend its own probe because the agency wants government investigators to interview executives and other potential witnesses before anyone from WorldCom talks to them to avoid potential witness tampering.

"Justice wants to go first. They want to get to people and get their version of events," the paper quoted an unidentified source it said is familiar with the investigation.

A WorldCom spokesperson wouldn't comment on either Journal report, but William McLucas, the attorney heading the internal investigation of WorldCom, told CNNfn Friday that he has not been asked to stop or delay his work. He said that the company's investigators have, "been in communication with the Department of Justice since day one and they have not asked us to halt the investigation." McLucas is former chief of enforcement for the SEC.

The company revealed last week that $3.8 billion of expenses were improperly reported as capital expenditures in 2001 and in the first quarter of this year, and it announced the firing of Chief Financial Officer Scott Sullivan. Investigators are looking at who else at the company knew of the improper accounting actions.

On Monday WorldCom said in a filing with the Securities and Exchange Commission that it was looking at whether to expand its restatement of results to 1999 and 2000.