NATO members are set to agree to a goal to increase their defense spending level to 5% of their GDP as a means to address a long-held grievance by President Donald Trump.

Secretary of State Marco Rubio said Thursday all NATO nations "will have agreed on a goal" of reaching 5% in defense spending over the next decade by time the military alliance has held its summit next month.

Slovenia and several NATO member states are seeking ways to expand the definition of defense spending as they attempt to meet US calls to allocate more funds on security, the nation’s prime minister said.