NATO defence ministers are expected to agree this week to a joint initiative aimed at improving the alliance's ability to respond quickly to new threats, NATO Secretary General Jens Stoltenberg said Wednesday.

The plan follows successive rounds of ramping up NATO's defence abilities in recent years in response to perceived aggression from Russia following its 2014 invasion of Ukraine's Crimean peninsula and support for separatists in eastern Ukraine.

The initiative, dubbed the ‘Four Thirties,’ would enable NATO to mobilize 30 land battalions, 30 air squadrons and 30 combat vessels within 30 days. It would comprise around 30,000 troops, 300 aircraft and at least 30 navy vessels or submarines.

‘High readiness is essential in a more unpredictable world,’ Stoltenberg said.

The NATO chief also confirmed that ministers are due to approve the establishment of new command centres in the German city of Ulm and in Norfolk in the United States.

‘These will be key to move our troops across the Atlantic and within Europe without delay, whenever needed,’ Stoltenberg told journalists.

The defence ministers' meeting will take place at NATO's new Brussels headquarters on Thursday and Friday, in preparation for a summit of NATO leaders next month.

However, the talks could be overshadowed by tensions between the transatlantic partners, after Washington's recent decision to impose tariffs on European steel and aluminium imports.

‘There are now serious disagreements between NATO allies on serious issues,’ Stoltenberg said, adding that the alliance must overcome its differences, as it had on previous occasions.

‘I believe it is possible to limit the repercussions,’ the NATO chief said.