Members of the Western military alliance have drained their stocks sending shipments of heavy ammunition to help Ukraine's forces battle Russia in a brutal war of attrition.

The latest deals -- signed with French firm Nexter and Germany's Junghans Microtec -- are estimated by officials to cover around 220,000 shells and deliveries to NATO members will start at the end of 2025.

"It is important that our allies refill their own stocks as we continue to support Ukraine," NATO chief Jens Stoltenberg said.

The US-led alliance last year launched a plan to bolster defence production and has since inked joint procurement contracts for ammunition worth some $10 billion.

Those include a deal to buy up to 1,000 European-produced Patriot air defence missiles that was signed last month.

The European Union has also launched its own efforts to increase defence production, but the 27-nation bloc is falling far short of a target of supplying Kyiv one million artillery shells by March.

The push to refill stocks and ramp up output comes as doubts swirl over future support for Ukraine from key backer the United States.

Stoltenberg insisted that Kyiv's supporters "will support Ukraine with the systems and the weapons and ammunition they need to prevail as a sovereign, independent country."

He said the alliance for now did not "see any direct or imminent threat against any NATO ally" from Russia and had stepped up its eastern defences to dissuade Moscow from any aggression.