DETROIT (AFP)--Struggling U.S. automaker General Motors Corp. (GM) appears unlikely to reach key agreements ahead of a March 31 deadline after its union and bond-holders went public with a spat over concessions.

"We don't think GM will be able to meet certain objectives by the deadline," Standard & Poor's Equity Research Services analyst Effraim Levy wrote in a research note Tuesday.

The United Auto Workers union and bond-holders are "playing cat and mouse about accepting equity in lieu of cash until they see what the other stakeholders get," Levy said.

GM is under pressure to hammer out a deal with its union and bond-holders to reduce operating costs and trim benefits as part of its bid to restructure under the government's multi-billion-dollar bailout package.

Levy said he expects the union to reach an agreement by the deadline but noted "resistance from GM bond-holders with nearly $30 billion in debt (principle amount) to swapping that debt for GM shares worth about one-third that amount."

But a union source close to the talks said negotiations with GM are being held up by a lack of sufficient sacrifices on the part of bond-holders.

The source also warned that "time is an issue" and noted it takes about seven to 10 days to get an agreement ratified by members.

The disagreement went public last week when the UAW's legislative director, Alan Reuther, complained in a letter to legislators that bond-holders were demanding additional sacrifices from retirees that go "beyond those called for by the terms of the loan agreements."

The ad hoc committee of GM bond-holders responded with a statement suggesting the pensioners were at the root of GM's problems.

They stepped up their offensive Sunday with a letter warning the presidential task force on the automotive industry that the government's proposal wouldn't be accepted by a sufficient number of bond-holders.

"The result of such a failed exchange would likely be a bankruptcy that would have dire consequences for the company, the tens of thousands of hard-working Americans that GM employs and the economy as a whole," the committee wrote.

GM is currently funding its operations with a $13.4 billion loan and has asked the U.S. Treasury for another $16.4 billion to weather a collapse in auto sales amid a deepening economic crisis.

GM spokesman Tom Wilkinson declined to comment on the letter or the status of negotiations "except to say that GM remains committed to concluding its balance sheet restructuring on an expedited basis."

While the Treasury has used the specter of a GM bankruptcy to try to pressure bond-holders to reach a deal, industry observes said it was unlikely that the government will let the largest U.S. automaker fail.

Steve Rattner, the lead advisor to the auto task force, appeared to back off the March 31 deadline in a series of recent interviews in which he criticized bond-holders for being "difficult" and warned that GM and Chrysler could need "considerably more" aid than they have already asked for.

Ford, the third automaker in Detroit's "Big Three," said it will attempt to weather the economic storm without government bailout funds.

On Thursday the Treasury released $5 billion to prop up auto suppliers in a move that was interpreted as a sign that the administration wasn't prepared to force GM into bankruptcy.

"It wouldn't make any sense to help the suppliers and not help the automakers," said U.S. congressman Thaddeus McCotter of Michigan.

But government support and a thoughtful restructuring plan might not be enough to save GM if auto sales don't improve soon, warned Rebecca Lindland, an analyst with IHS Global Insight.

"The threat of GM going bankrupt still is very real," she said in a telephone interview.

"We can continue to throw billions of dollars at those companies, but until the American consumer starts spending again it's not going to help."