The defense ministers of Europe's five top military spenders have said they want to continue increasing their investments in defense but described meeting President-elect Donald Trump's challenge for them to raise spending to 5% of their overall economic output as complicated.

The defense ministers of Germany, France, Britain, Italy and Poland came together Monday near Warsaw for a meeting in a new format that they established after Trump was re-elected last year. Their first meeting in this format of five NATO members was held in Berlin in late November.