WASHINGTON – President Barack Obama on Monday proposed reining in expenses at NASA, sending his 2012 budget blueprint to Congress calling for a five-year freeze on new spending at the US space agency.

The president would restrict NASA's budget to last year's levels, $18.7 billion annually through fiscal 2016. The figure represents a 1.6-percent decrease from the spending total the agency had sought for fiscal 2011, which ends in September.

"This budget reflects the overall fiscal reality of the US government. There is not a lot of money available," said John Logsdon, a former director of the Space Policy Institute in Washington.

"It should not compromise what NASA wants to do but it certainly would slow it down," said Logsdon, an independent consultant to the Obama administration. "They intend to do everything, just it will be a slightly slower schedule."

A final US budget for fiscal 2011 has not been approved because Democrats and Republicans failed to agree on spending levels in the runup to last November's mid-term election. At that time, Obama and fellow Democrats decided to maintain 2010 levels.

But Republicans won control of the House of Representatives and they are vowing massive spending cuts for the remainder of fiscal 2011 and beyond.

One administration official, close to the National Aeronautics and Space Administration and speaking anonymously, said: "We don't know what NASA will get in 2011."

Nearly half of Obama's proposed 2012 NASA budget -- and for the next five years -- is dedicated to space operations and exploration systems including $2.9 billion for the development of a heavy launcher and a space capsule intended for missions beyond low Earth orbit.

The heavy launcher will be crucial for sending astronauts to an asteroid of Mars, but also to the International Space Station, as the agency's space shuttle program winds down this year.

Seven billion dollars have been earmarked for work aimed at making the new heavy launcher operational by 2016.

But NASA has not yet determined the architecture of the system nor when it will be operational. The goal of 2016, in any case, is unlikely.

A major theme of this budget is to maintain access for American astronauts at the International Space Station whose use has been extended to 2020.

After the final flights of the three-decade-old space shuttle program, the United States would depend on Russia's Soyuz spacecraft to carry US astronauts to the ISS until a successor to the shuttle is developed.

Obama's budget would continue to push for commercial partnerships to develop reliable access to the ISS and lessen the reliance on Russia.

But with voters fed up with government spending, the end result is anyone's guess.

"You cannot predict what is going to happen," Logsdon said. "The new conservative Republicans are going to say there is too much money for space and you have to cut more."