The White House announced on Monday that it was adding $4 billion to a list of proposed tariffs that would be placed on European Union products as part of a long-running dispute over aviation industry subsidies. The items targeted ranged from metals and chemicals to agricultural products, such as fruits, dairy, coffee, and pork.

"This supplemental list adds 89 tariff subheadings with an approximate trade value of $4 billion to the initial list published on April 12, which included tariff subheadings with an approximate trade value of $21 billion. USTR is adding to the initial list with the supplemental list in response to public comments and additional analysis," the U.S. Trade Representative's Office said in an announcement Monday.

The U.S. and EU have been fighting since 2004 over whether their respective aerospace industry policies towards Airbus and Boeing amount to unfair practices. The World Trade Organization said earlier this year that the U.S. had failed to eliminate subsidies for Boeing. The alleged subsidy was a $100 million tax break given to Boeing from Washington state, not a federal government policy. Last year, the WTO found that the EU had been providing illegal subsidies to Airbus, and the USTR has estimated the economic harm from those subsidies at $11 billion.

WTO arbitrators have yet to set an amount in either case. A final ruling by the WTO in the Airbus case could come by the summer. A ruling in Boeing one isn't expected until next year.

The U.S. and EU have tentative plans to meet this year to resolve trade differences but the talks have yet to be scheduled and are bogged down over what issues will be discussed. The U.S. wants agricultural subsidies to be up for negotiation, but EU officials have repeatedly ruled that out.