The European Union’s promise to buy $750 billion of American energy imports over three years was pivotal to securing a trade deal with President Donald Trump, but it’s a pledge it will struggle to keep.

The energy deal is a centerpiece of the trade agreement reached between Washington and Brussels on Sunday, which puts baseline U.S. tariffs at 15% for most European goods. The EU has agreed to buy $250 billion worth of U.S. oil, gas and nuclear fuels per year for three years, European Commission President Ursula von der Leyen said.

The EU's energy spending goal is deemed unrealistic. The EU is committing to purchase $750 billion worth of U.S. oil and gas before Trump leaves.