Brussels, June 15 -- : In a show of unity ahead of meeting with Russian President Vladimir Putin, US President Joe Biden on Monday (local time) said that the North Atlantic Treaty Organisation (NATO) treaty is rock solid and unshakable.

He then called Putin a bright, tough and worthy adversary.

"The NATO treaty is rock solid and unshakable. It's a sacred commitment," Biden told reporters after meeting with allies at the headquarters of the 30-member military alliance that has long been focused on the threat posed by Russia.

"Putin is bright, he is tough and I have found that he is... a worthy adversary," he said while hailing Putin.

In a White House statement, the US President said:"There is a growing recognition over the last couple of...