WASHINGTON – A breakdown in high-stakes budget talks in Congress could threaten plans for a missile defense shield in Europe.

Congressional negotiators have shown little sign they will be able to meet Wednesday’s deadline for reducing the deficit by $1.2 trillion over 10 years. If they fail to agree, a new law mandates cuts throughout the federal government, including a big slice of the defense budget.

While it is not known what military spending would be cut, an expensive program aimed primarily at defending Europe is unlikely to be spared.

The United States sees the missile defense system, aimed at countering a threat from Iran, as part of its contribution to the NATO military alliance.

With the United States often complaining that it makes a disproportionately large contribution to NATO, missile defense could be especially vulnerable to budget-cutters.

“A missile defense system for NATO? It’s going to be hard to keep people committed if they think the U.S. is picking up the tab for Europe,” said Kurt Volker, who was ambassador to NATO at the end of the George W. Bush administration.

Defense Secretary Leon Panetta has warned that the European missile defense program could be threatened if the special deficit reduction committee should fail to work out a deal.

That suggestion, though, may have been intended mostly to nudge lawmakers to resolve their differences and avoid the automatic cuts to one of their favorite programs.

It is still possible that committee members could set aside intense partisan differences and reach a deal by Wednesday.

And even if they do not, Congress might find a way to cancel the cuts before they take effect in 2013.

But that may only delay scaling back the U.S. military role in Europe.

A decade-long expansion of military spending appears to be coming to an end, and the Obama administration has indicated it is shifting its foreign policy toward Asia, where it sees the greatest opportunities and threats of coming decades.

Beyond missile defense, the automatic cuts could prompt the U.S. to save money by shifting some warships away from Europe but probably would not lead to fewer U.S. troops there.