The European Union insisted Tuesday it will enforce a new law that imposes an emissions cap-and-trade program on airlines flying to and from Europe, despite angry opposition from the U.S. Congress.

"We do not intend to modify our adopted legislation (but) the commission is of course open to discuss other partners' concerns on how we will implement our legislation," said Isaac Valero-Ladron, spokesman for the EU's climate agency.

Starting Jan. 1, the EU plans to include all airlines flying to and from its 27 member countries in its cap-and-trade program - a move that will eventually force the carriers to pay for their emissions of carbon dioxide, a so-called greenhouse gas that contributes to global warming. The restrictions are designed to encourage airlines to switch to cleaner fuels or economize on fuel consumption.

The move is opposed by airlines from the United States, China, Russia, Japan, Brazil and elsewhere. They have argued that the EU cannot impose its rules on flights that originate outside its territory.

And the International Air Transport Association has called for the UN aviation agency to step in and provide a global program.

Earlier this month, Europe's top court rejected a complaint by U.S. and Canadian airlines that the legislation breaches international law.

On Monday, the U.S. House of Representatives voted to exclude U.S. airlines from participating in the EU program. The measure directs the transportation secretary to prohibit U.S. carriers flying to and from Europe from participating in the program if it is unilaterally imposed. It also tells other federal agencies to take steps necessary to ensure that U.S. carriers are not penalized by the emissions control scheme.

The bill now goes to the Senate, where there is currently no companion legislation.

American lawmakers described the program as a "tax grab" because it includes all carbon dioxide emissions from the airliner's point of departure or arrival -- including over the Western Hemisphere and the Atlantic Ocean -- rather than just those in European airspace.

Connie Hedegaard, the 27-nation bloc's climate action commissioner, said she expected the United States to respect EU law, "just like the EU always respects U.S. law."

"Why else would U.S. airlines have brought the issue to court?" she said.

Meanwhile, the Air Transport Association of America, which represents the big U.S. airlines, urged the EU to back down so that international airlines don't have to be put in a position of not to complying with the law.

"We think the Europeans should think hard and withdraw the scheme," said Nancy Young, the association's vice president of environmental affairs.