By Kevin Krolicki - Analysis DETROIT (Reuters) - General Motors Corp is battling to survive collapsing auto demand, tight credit and uncertain prospects for recovery in its biggest markets. But its most-pressing crisis is simpler: too much debt. As GM begins a second round of make-or-break concession talks with creditors and its major union, analysts and bondholders are raising concern its restructuring plan does not go far enough to scour its balance sheet. The risk is that even if GM wins the high-stakes deals it needs to eliminate some $28 billion in debt by issuing new shares, it could end up wiping out those gains by borrowing even more from the U.S. government. Bondholders worry that would leave the automaker vulnerable to a second and even-more wrenching restructuring -- only this time they would be the equity owners of the ailing company. 'Everybody is going to have to give at the office to make this work,' said a person with direct knowledge of GM's talks with bondholders. 'But this would leave bondholders behind a monstrous debt claim.' Analysts warn that the risk of bankruptcy remains large. A day after GM submitted its restructuring plan to U.S. officials, ratings agency Moody's Investors Service put the risk that GM or Chrysler LLC, or both, are forced into bankruptcy at 70 percent, unchanged from its view in December. The issue of GM's debt load as it fights to restructure outside bankruptcy will be central to a high-pressure round of negotiations between GM and its bondholders now set to begin. GM bondholders, led by a committee of big investors, are being asked to cut the $27 billion they are owed by two-thirds in exchange for shares in a recapitalized automaker. The other $18 billion in bond debt would disappear from GM's balance sheet. That equity-swap could give bondholders a stake of some 65 percent of the new GM that the automaker hopes will emerge from its 'Renaissance' plan, according to an early estimate from Credit Suisse analyst Chris Ceraso. The talks will have to be wrapped up around the third week of March to launch the equity exchange by March 31 as mandated by GM's bailout, the person close to the talks said. That leaves GM with about five weeks to conclude negotiations on three fronts: It needs deals with bondholders and its union on debt concessions and an agreement with the government's auto restructuring panel headed by Treasury Secretary Timothy Geithner on funding. Failure on any front risks bankruptcy.