The so-called "Bucharest Nine" countries, which first held talks in Romania in 2015, also includes Bulgaria, the Czech Republic, Estonia, Hungary, Latvia, Lithuania, Poland and Slovakia.

The group believes it is necessary to supplement NATO's current ground forces "with aerial and naval components" to "achieve the full spectrum," Duda told reporters alongside his Romanian counterpart Klaus Iohannis.

The B9 presidents adopted a joint statement in which they called on the US-led alliance to discuss the increased presence at next month's NATO summit in Brussels.

They also requested that NATO deliver a response to what the West calls Russian "hybrid warfare" techniques, which include military, financial and political manipulation backed by computer hacking and propaganda.

NATO beefed up its defences in central and eastern Europe in response to growing fears about Russia, following Moscow's annexation of Crimea in 2014.

"The 2018 NATO summit should further strengthen the Alliance's unity and, in the spirit of the 360-degree approach, deliver a comprehensive response to the current security challenges, including against the hybrid threats the allies are confronted with," the B9 statement said.