NATO chief Jens Stoltenberg said Wednesday that alliance members must guarantee long-term weapon deliveries for Ukraine, as ministers prepared to discuss a proposal for a 100-billion-euro, five-year fund.

"We must ensure reliable and predictable security assistance to Ukraine for the long haul so that we rely less on the voluntary contributions and more on NATO commitments, less on short-term offers and more on multi-year pledges," Stoltenberg said as NATO foreign ministers met in Brussels.