The Latest on the NATO summit on Friday and Saturday (all times local):

4:10 p.m.

NATO's secretary-general says the alliance has reached a "defining moment for our security" and will meet the challenge head-on at its summit this week.

"The world is a more dangerous place than just a few years ago," Jens Stoltenberg said Thursday. "NATO is responding, with speed and with determination."

A two-day meeting of NATO heads of state and government begins in the Polish capital Friday.

"Tomorrow and Saturday we will take new, major steps" to ensure NATO member nations' security and help foster stability in the Middle East and North Africa, Stoltenberg told a joint news conference held with Polish President Andrzej Duda.

"It is fitting that we meet in Warsaw, a city that knows the pain of conflict and the value of security," added Stoltenberg in a reference to Poland's tumultuous history.

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4:05 p.m.

NATO leaders meeting in Warsaw Friday and Saturday will recognize cyberspace as an official "operational domain" for alliance activities, along with air, land and sea.

Bogdan Botezatu, an analyst for Bitdefender, a Romanian global security technology company, says "cyberspace is basically now a battlefield along with air, sea, and land."

Bitdefender worked on cybersecurity for Ukraine in 2014 after NATO assigned Romania to upgrade security there.

He says there were five threats targeting France, Germany Spain and Romania last year, each focused on a specific area such as diplomatic relations, airspace or finance.