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.

The Netherlands remains hopeful that Spain will drop its opposition to a proposed increase in NATO defense spending, as all 32 member states prepare to meet in The Hague next week to reach a crucial agreement on raising the alliance’s defense budget target from 2 percent to 5 percent of gross domestic product (GDP).

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