WASHINGTON — U.S. President Barack Obama’s plan to send humans to visit an asteroid by 2025 has taken a backseat to budget pressures that threaten NASA research and development programs needed to realize that vision.

“He mentioned that in a speech back in April, but really the budget priorities have now changed,” Benjamin Neumann, director of the Advanced Capabilities Division in the Exploration Systems Mission Directorate at NASA headquarters here, told Space News following remarks at a Feb. 22 workshop on near-Earth objects (NEOs) and human exploration beyond low Earth orbit.

Neumann was referring to Obama’s April 2010 speech at NASA’s Kennedy Space Center in Florida, where the president said his administration would develop the capabilities to send U.S. astronauts to an asteroid by 2025. Earlier in the year Obama moved to dismantle the 5-year-old Constellation program, which was aimed at returning astronauts to the Moon.

“We’ll start by sending astronauts to an asteroid for the first time in history,” Obama said in his speech. “By the mid-2030s, I believe we can send humans to orbit Mars and return them safely to Earth.”

A few months earlier, Obama had called for spending $3 billion over five years on robotic precursor missions in the 2011 budget blueprint he sent lawmakers last February, including $125 million in the current budget year and a projected $506 million in 2012.

The funding was intended in part to pay for precursor missions that could scout candidate asteroids for future manned missions. However, in the 2012 NASA spending plan Obama sent to Capitol Hill Feb. 14, the proposed funding for robotic precursor missions in 2012 was zeroed.

Neumann said NASA is still grappling with funding issues in the current budget year as Congress continues to debate the president’s 2011 spending request. As a result, he said the agency is not well-positioned to plan for future surveys of NEOs as mandated in a 2005 authorization act, nor can it embark on development of robotic precursor missions.

“I’m not going to debate about [20]12 and why is the budget not prioritizing things differently,” he said in the interview. “I’m not even ready to tell you what our priorities are from appropriations this year.”

Despite Congress’ lack of action on the president’s 2011 funding request, which leaves NASA and other government  agencies operating at the lower spending levels appropriated for 2010, Neumann said the agency is also working to meet requirements laid out in the NASA Authorization Act of 2010. That law calls on NASA  to get started immediately building a new heavy-lift launch vehicle and crew capsule that leverage investments in the space shuttle and in Constellation.

“There are some practical issues about do we need a crew vehicle, do we need a heavy-lift [vehicle],” he said. “If we don’t get those what will our human exploration missions be like? I think the answer right now is we better get that transformation from Constellation to this new capability and get it in place first.”

However, Neumann said the five-year projections accompanying Obama’s 2012 spending plan include around $20 million for the Exploration Systems Mission Directorate and a similar amount for the Science Mission Directorate to collaborate on robotic precursor initiatives with other countries starting in 2013.

“We are both incentivized that way,” he said. “It’s money we could use to build instruments to put on someone else’s spacecraft, a mission of opportunity. We just started to look at it; it’s not part of the 2012 plan, so we’ll need to see.”

Sam Scimemi, deputy for NASA’s international space station program at agency headquarters here, was less optimistic.

“We have lots of viewgraphs, lots of analysis, hell we’ve been dreaming for 60 years about leaving low Earth orbit and leaving the environs of the Moon. But we have not been able to put together a program that’s sustainable to get us there,” he said in remarks during the workshop. “Getting to a NEO is going to cost billions of dollars if you want to send people to it. So we’re going to have to find a policy and political construct based on the technical aspects you talked about here today that bridges that gap.”