* Obama budget draws criticism from Republicans

* Budget leaves details on healthcare, energy for later

* New Democratic Senator Specter votes against budget (Updates with Senate vote)

By Jeremy Pelofsky

WASHINGTON, April 29 (Reuters) - The Democratic-controlled U.S. Congress on Wednesday approved a $3.4 trillion compromise budget plan for the 2010 fiscal year, clinching a big victory for President Barack Obama on his 100th day in office but with no Republican support.

The nonbinding plan sets parameters for spending and tax legislation for the upcoming fiscal year that begins on Oct. 1 and mirrors most of what Obama had sought, but Republicans blasted it for exploding the debt and undermining the ailing economy.

Obama has argued that the budget and the $787 billion economic stimulus package were necessary to heal the economy and reverse what he says has been neglect of programs like education and healthcare.

"This budget was hugely important to the president, this is the starting point for everything he wants to do," Democratic Senator Kent Conrad, the chairman of the Senate Budget Committee, told reporters.

"For every one of his key priorities, reducing dependence on foreign energy, making possible healthcare reform, a focus on excellence in education, none of those things could have been pursued effectively without this budget," he said.