Under the 1997 NATO-Russia Founding Act, the Alliance promised not to permanently station substantial forces in Eastern Europe and the Baltic states.
"The 1997 agreement was signed with a different Russia. The Russia it was signed with no longer exists; today's Russia is a Putinist Russia," Landsbergis said at a joint news conference with his Icelandic counterpart in Vilnius.
"We are not bound by any legal obligations with the state under the current regime," the Lithuanian minister said. "This is the way we have to look at it if we are talking about the creation of bases and military build-up. We are not bound by that agreement."
According to Landsbergis, the Kremlin itself is to blame for this.
"Putinist Russia has done everything to make this happen," he said.
Icelandic Foreign Minister Thordis Kolbrun Reykfjord Gylfadottir said that she broadly shared her Lithuanian counterpart's view.
"I think that there is not much to build on when it comes to agreements with Russia because of obvious reasons," she said.
NATO's summit in Madrid this summer will set the future direction of the Alliance's posture, according to the Icelandic minister.
"Security in Eastern Europe is changed. Even if we see the end of this brutal war soon, we will have a totally different situation when it comes to security," she said.
The Madrid summit is expected to update the Alliance's defense strategy in response to Russia's threat.
Member states' commitments to increase defense spending are also expected to be discussed at the summit.
Western countries are taking these steps after Russia's forces invaded Ukraine in late February.