Correspondents say there is no immediate threat to the government, but the DMK pullout will make it more difficult for it to pass legislation - the Congress party is dependent on several regional allies for support in parliament.
Calyon Securities analyst Raymond Neidl said the outcome is entirely dependent upon Washington and whether or not it believes such a merger could pass antitrust standards.
Consumers and businesses need reliable supplies of energy to make our economy run so I urge you to pass legislation to modernize our electricity system, promote conservation, and make America less dependent on foreign sources of energy.