BERLIN Germany is ready to deploy a robust brigade of some 4,000 troops to Lithuania permanently, in coordination with NATO's rethink on defence of its eastern flank in light of Russia's invasion of Ukraine, Germany's defence minister said on Monday.

"Germany stands by its commitment as a NATO member, as Europe's biggest economy, to stand up for the protection of the eastern flank," Pistorius said during a visit to Vilnius on Monday, without giving a timeline.

In the past, Berlin said it would take Lithuania years to provide barracks, housing areas for the families, depots and sufficient training grounds.

"Precondition (for the deployment) is that the necessary infrastructure is in place," he told reporters on a visit to Lithuania.

Germany already leads NATO's multi-national battlegroup in Lithuania, a reinforced battalion of some 1,000 troops, meant to strengthen the alliance's eastern flank.

Beyond this, a German brigade is on stand-by in Germany to rapidly reinforce troops in Lithuania if needed. Vilnius, however, has long demanded the permanent presence of a full German brigade.

"We agree that the brigade will grow step by step as the infrastructure is established," Pistorius noted, adding that such a deployment could not be completed within "a few months".

The endeavour must be compatible to NATO's regional plans detailing how the alliance would respond to a Russian attack, the minister stressed, referring to documents recently drawn up for the first time since the end of the Cold War.

Pistorius and NATO Secretary-General Jens Stoltenberg travelled to Lithuania to attend an exercise that will test the swift reinforcing of the existing German-led NATO battlegroup to the size of a brigade, a scenario to be enacted in case of heightened tensions or a conflict with Russia.

On July 11-12, NATO leaders will meet for a summit in Vilnius.

(Reporting by Sabine Siebold; editing by Matthias Williams and Frank Jack Daniel)