Qwest Communications International Inc. (Q) boosted its offer for MCI Inc. (MCIP) to $8.94 billion Thursday, adding $500 million to its bid to wrest the long-distance phone company away from Verizon Communications Inc (VZ).

The latest offer, delivered two days after MCI agreed to a sweetened $7.51 billion deal with Verizon, was equal to $27.50 per MCI share.

It also boosted the cash portion of the offer to $13.50, or $4.4 billion, while offering additional protection against a decline in the Qwest shares being used for the balance of the payment. Qwest's prior bid of $25.60 per share included $10.10 in cash, or a total of $3.3 billion.

Qwest CEO Richard Notebaert (search) set a Monday deadline for the board to respond before the offer would be withdrawn.

Soon after the new Qwest bid was disclosed, The Wall Street Journal reported that Verizon was exercising its right to hold a vote by MCI investors on the merger before a special shareholder meeting scheduled in May for that purpose. Verizon spokesman Eric Rabe declined comment.

MCI spokesman Peter Lucht said the board will review Qwest's latest offer and "respond accordingly."

Shares of MCI jumped for a third straight day amid the biggest telecom bidding war since 1999, at the height of the technology boom. The stock rose 56 cents, or 2.3 percent, to $25.01 in afternoon trading on the Nasdaq Stock Market.

But Qwest's shares slid 4.5 percent, 17 cents to $3.60, on the New York Stock Exchange, while Verizon 's rose 20 cents to $35.63.

The new deal with Verizon, the dominant local phone company in the eastern United States and a top wireless operator, values MCI at $23.10 per share.

In a letter to MCI's board, Qwest's Notebaert said, "We were particularly dismayed that MCI did not contact us to discuss our willingness to adjust our offer prior to signing the amended merger agreement, a step MCI deliberately chose not to take even though it certainly could have benefited shareholders."

Qwest and Verizon have been battling for more than six weeks for MCI, the Virginia-based company formerly known as WorldCom.

MCI's board has been concerned about partnering with Qwest, questioning its financial health and ability to compete against larger, well-healed rivals such as Verizon and SBC Communications Inc. — which set off the scramble for MCI with a deal to acquire AT&T Corp. two months ago.

Denver-based Qwest, with local phone service in 14 mostly Western states and a nationwide fiber-optic network, is weighed down by $17 billion in debt and lacks a wireless division.

MCI has far less debt, but like AT&T is steadily losing revenues and customers with the collapse of long-distance phone service as a viable standalone business.

Both long-distance companies, however, retain valuable assets with their millions of customers, especially high-paying businesses, as well as national fiber-optic networks.