Legislation passed May 25 by the U.S. House of Representatives could make it more difficult for NASA to get relief from a 2000 law barring the U.S. space agency from buying Soyuz crew capsules and other goods and services from Russia.

NASA needs to start paying for Soyuz vehicles if it wants U.S. astronauts to participate in extended stays aboard the international space station after April 2006, when an agreement granting NASA free use of the Russian-built hardware finally expires.

The Iran Nonproliferation Act (INA) of 2000, enacted to curb the flow of weapons technology to Iran, prohibits NASA from buying international space station-related goods and services from Russia as long as the White House remains unable to certify to Congress that Russian aerospace entities have stopped giving aid to Iran.

The House Armed Services Committee now has sent a strong signal that it will oppose any effort to water down that law for NASA’s sake. That message was delivered in its version of the National Defense Authorization Act for 2006 (H.R. 1815), which passed by a vote of 390-39. The bill provides $441.6 billion in budget authority for the U.S. Defense Department and national security programs managed by the U.S. Department of Energy.

Section 1211 of the bill, “Report on Acquisition by Iran of Nuclear Weapons,” calls the Iran Nonproliferation Act “a critical tool” in preventing the Islamic Republic from obtaining weapons of mass destruction and warns that the act “should not be weakened by creating exceptions . . . that are intended to serve lesser policy priorities.”

A congressional aide said the language was added to the defense bill by nonproliferation hawks determined to send a message to NASA and the White House that keeping American astronauts aboard the international space station must take a distant back seat to preventing Iran from getting weapons of mass destruction.

“It was definitely meant as a shot across the bow,” the aide said.

The Senate version of the defense authorization bill, which cleared the Senate Armed Services Committee in mid-May and now awaits a vote on the floor, includes no language on the Iran Nonproliferation Act.

A report from the Congressional Research Service published in March warned that while it is unlikely that U.S. President George W. Bush would give Russia a passing grade in nonproliferation , it may be equally unlikely that the law would be repealed or amended in the current political atmosphere.

The White House has been contemplating changes to the Iran Nonproliferation Act that would permit Soyuz purchases, according to government sources. But the administration has yet to send Congress a written legislative proposal, these sources said.

John Logsdon, director of the Space Policy Institute at the George Washington University here, said the language in the House version of the defense authorization bill does not necessarily preclude an eventual Soyuz deal.

“It seems to me that we have to wait to see what the White House proposes as a way around this knotty problem before throwing in the towel on obtaining additional Soyuz. This House action just underlines an already well-recognized congressional concern,” Logsdon said, noting that House Science Committee Chairman Sherwood Boehlert (R-N.Y.) “said basically the same thing last February.”

With NASA Administrator Mike Griffin determined to retire the space shuttle by the end of 2010, even if that means trimming the number of space station assembly flights from 28 to 18 or fewer, there are changes ahead for the space station program that will affect all of NASA’s partners, particularly Europe and Japan. Both nations are counting on the shuttle to launch their station hardware.

Logsdon said much negotiating remains to be done, both inside the U.S. government and internationally with NASA’s space station partners, before everything is sorted out.

“There is lots of domestic and international bargaining, and some compromises, ahead to bring [international space station] assembly to a state minimally satisfactory to all parties to the project,” Logsdon said.

By the time all is said and done, according to Logsdon, it is possible that the Soyuz issue could work itself out without changes to the Iran Nonproliferation Act.

Brian Berger is editor in chief of SpaceNews.com and the SpaceNews magazine. He joined SpaceNews.com in 1998, spending his first decade with the publication covering NASA. His reporting on the 2003 Space Shuttle Columbia accident was...