The United States is to cut its contribution to NATO's operating budget, officials said Thursday, with Germany increasing payments as the alliance tries to appease President Donald Trump ahead of a summit next week.

Trump has repeatedly criticised European members for freeloading on the US, singling out Germany - the continent's economic powerhouse - for lagging behind on an alliance commitment to spend at least two percent of GDP on defence.

While most of Trump's anger has been focused on European national defence budgets, American officials have also grumbled about how much Washington contributes to NATO's running costs, and the 29-member alliance has now agreed to a change.

"All allies have agreed a new cost-sharing formula. Under the new formula, cost shares attributed to most European allies and Canada will go up, while the US share will come down," a NATO official said.

"This is an important demonstration of allies' commitment to the alliance and to fairer burden-sharing."