The flights "will enhance the Alliance's situational awareness," a NATO official said, adding: "All AWACS reconnaissance flights will take place solely over Alliance territory."
"This decision is an appropriate and responsible action in line with NATO's decision to intensify our ongoing assessment of the implications of this crisis for Alliance security," the official said.
The NATO announcement comes as Washington and Moscow traded barbs over rival proposals to ease the crisis, with each challenging the other to show they were really interested in a peaceful outcome.
The AWACS aircraft are one of the most sophisticated command and control vehicles in the NATO armoury, capable of monitoring huge swathes of airspace.
More From This Section
Diplomatic sources said the AWACS were routinely deployed and on that count, there was nothing unusual in their use in this case.
However, it was unusual for their deployment to be announced publicly in this way, they said.
Flying over Poland and Romania, the AWACS planes, with their distinctive rotating radar dome mounted above the fuselage, should be able to see far into Ukraine airspace.
The situation risks becoming more difficult if Crimea, now controlled by pro-Russian leaders, votes in a March 16 referendum to break all links with Kiev and become part of Russia.
Poland and the Baltic states especially have taken a hard line as events have unfolded and last week, Warsaw called for urgent consultations with its NATO allies on the situation.
In response to Putin's move into Crimea, home to a large Russian-speaking population and the Black Sea fleet, the US is sending a dozen F-16 fighter jets and 300 service personnel to Poland as part of a training exercise.