BRUSSELS, March 22 (Xinhua ) -- Ukraine crisis is a "game-changer" for NATO allies who must strengthen their economic and military ties, NATO Secretary General Anders Fogh Rasmussen said in a speech at the Brussels Forum on Friday.

The Secretary General set out three priorities as he called on allies to reaffirm their "commitment to collective defence, strengthen support to Ukraine and the wider region, and to make clear that we can no longer do business as usual with Russia."

Rasmussen said the September NATO Summit in Wales will be a key one for allies to ensure they have the full range of capabilities to deter and defend against any threat.

The Brussels Forum, organized by the German Marshall Fund of the United States, is an annual high-level meeting of the most influential North American and European political, corporate, and intellectual leaders to address pressing challenges currently facing both sides of the Atlantic.