"We face intensifying threats from 'state-based aggression,' from rogue nations like DPRK and Iran to revisionist powers as different as China and Russia… We value the U.K.’s diplomatic, moral and military leadership on the European and global stages, particularly as Russia seeks to undermine and weaken NATO’s cohesion and capabilities," Mattis told his UK counterpart.
READ MORE: Security Analyst: NATO Putting 'Unprecedented' Level of Pressure on Russia
The next meeting of NATO defense ministers is scheduled for February 14-15 at NATO headquarters in Brussels.
The United States, particularly as part of NATO, has been boosting its military presence in Europe since 2014, using the Ukrainian crisis as a pretext for the deployment of additional hardware near Russia's borders. Moscow called the actions provocative and warned that they could lead to regional and global destabilization.
READ MORE: Moscow Calls on US to Withdraw Nukes From European Territory
The US National Defense Authorization Act (NDAA) for fiscal year 2018 stipulates the allocation of $4.6 billion for the European Deterrence Initiative (EDI) to reassure NATO allies and enhance the US deterrent in Europe as well as improve the resilience of the Baltic nations against alleged Russian aggression.