British Defense Secretary Ben Wallace on Monday said 350 more British troops would be sent to the Polish border, to shore up NATO's eastern flank against any Russian aggression.

Wallace said the troops would strengthen a contingent of 100 British soldiers already there and would be a "bilateral deployment to show that we can work together and send a strong signal that Britain and Poland stand side by side".

The announcement came following talks between Wallace and Polish Defense Minister Mariusz Blaszczak amid Ukraine tension, which could spark a massive exodus of refugees into Poland.

Belarus last year allowed migrants to cross its border into Poland, sparking a humanitarian crisis and prompting the deployment of 100 British troops to strengthen the border.

Blaszczak told journalists that the additional British troops would "cooperate with the Polish armed forces on increasing the security, especially when it comes to the threats on the border".

Russia is seeking a guarantee from NATO that Ukraine will not enter the alliance and wants the bloc to withdraw forces from member states in eastern Europe.

Wallace on Monday insisted that NATO is a defensive alliance and that Russian aggression would be counterproductive and lead to "more NATO, the very thing that President Putin says he doesn't want".