President Obama vowed to defend his plan to mothball NASA's shuttle fleet as the debate over the spacecraft's future turned partisan.

The White House said Obama would explain to the country why he believes NASA would get more bang for its space buck by scrapping the shuttle and turning rocket launches over to private contractors in an address slated for April 15th.

"After years of underinvestment in new technology and unrealistic budgeting, the President's plan will unveil an ambitious plan for NASA that sets the agency on a reinvigorated path of space exploration," the White House said in a statement, according to Reuters.

The shuttle program is slated to end later this year.

Obama's proposed $3.8 trillion federal budget request, released last month, also strips funding for the Constellation program, which was to see NASA return astronauts to the moon by 2020.

It also would effectively outsource the transportation of astronauts to and from the International Space Station to the private sector.

Republican Senator Kay Bailey Hutchison, of Texas, last week slammed Obama's agenda, claiming it would cause the U.S. to take a back seat to other countries in terms of space research and exploration.

Bailey also said the shuttle program shouldn't be scrapped until a replacement vehicle is ready.

"We must close the gap in U.S. human space flight or face the reality that we will be totally dependent on Russia for access to space until the next generation of space vehicle is developed," said Hutchison.

"If the space shuttle program is terminated, Russia and China will be the only nations in the world with the capability to launch humans into space. This is unacceptable," said Hutchison.

Hutchison introduced a bill that would give the shuttle program a reprieve until NASA develops a replacement and extend the life of the International Space Station through 2020. The bill also calls for the U.S. government to develop a new space vehicle for human flight by 2015.

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