The success of a key NATO summit hung in the balance on Friday, after Spain announced that it cannot raise the billions of dollars needed to meet a new defense investment pledge demanded by U.S. President Donald Trump.

President Donald Trump criticized Spain for its lack of defense spending compared to other NATO countries. He suggested Spain has either been excellent at negotiating or not fulfilling its obligations.

Spain has rejected Donald Trump’s “unreasonable” demand that Nato members increase defence spending, throwing plans for a summit of alliance leaders into disarray.