The US Treasury Department on Tuesday slammed an EU ruling ordering Apple to pay record back taxes, saying the decision threatened the bilateral "spirit of economic partnership".
"The Commission's actions could threaten to undermine foreign investment, the business climate in Europe, and the important spirit of economic partnership between the US and the EU," a Treasury Department spokesperson said in a statement.
"We will continue to monitor these cases as they progress, and we will continue to work with the Commission toward our shared objective of preventing the erosion of our corporate tax bases."
The EU ruling ordered the US tech giant to repay Ireland a record 13 billion euros ($14.3 billion) in back taxes, finding that Apple had benefited from a series of Irish sweetheart tax deals that were illegal.
The Treasury Department roundly rejected the reasoning of the commission's decision, even as Apple and the government of Ireland both vowed to file appeals.
"While we decline to comment on specific cases, Treasury is disappointed that the Commission is acting unilaterally and departing from the important progress the US, the EU, and the rest of the international community have made together to combat tax avoidance," the statement said.
"As we have said, we believe that retroactive tax assessments by the Commission are unfair, contrary to well-established legal principles, and call into question the tax rules of individual member states.
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