A consortium led by Lockheed Martin Corp is continuing to work toward a fourth quarter 2013 flight test to prove its MEADS missile defense system can intercept a ballistic missile, although some U.S. lawmakers have sought to cut off funding for the three-nation program.

Officials with Lockheed and the MEADS International consortium, which includes partners from Italy and Germany, on Monday said they were “cautiously optimistic” that U.S. lawmakers would reach a compromise to allow funding for the final year of development on the missile defense program.

“There are many options that could result in a path toward the MEADS program being funded,” Mike Trotsky, a senior executive at Lockheed’s Missiles and Fire Control business, told Reuters on Monday. He said halting work on the test could lead to delays and budget problems later if lawmakers ultimately approved the funding.

President Barack Obama last week signed a $633 billion policy bill that authorizes funding for the U.S. military in fiscal year 2013 which began Oct. 1, despite concerns about some aspects of the bill, including its ban on MEADS funding.

The measure prohibits a final U.S. payment of $400.9 million for the last year of development work on the Medium Extended Air and Missile Defense System (MEADS), a joint ground-based missile defense program. The United States, Italy and Germany have spent about $4 billion to develop MEADS over the past decade as a successor to the Patriot missile defense system.

Lockheed, the Pentagon and officials in Italy and Germany are hoping that congressional appropriators, who control the actual funding for arms programs, will still allow the Pentagon to fulfill its final funding obligations for the program.

Otherwise, they argue, the U.S. government may face termination fees nearly equal to the money required to finish the system, and could lose access to the technologies developed under the international program.

Trotsky said the money slated for fiscal 2013 would pay for the intercept test and about 1,000 staff still working on the program in the three countries. It would also repay some money lent to the program in earlier years by Italy and Germany, he said. The program had about 2,000 workers at its height.

The White House has warned that banning funding for the MEADS program could harm Washington’s broader relationship with its allies, jeopardizing the kind of multinational projects favored by the Obama administration as budget pressures mount.