— The suspension of "all practical civilian and military cooperation" between NATO and Russia. NATO officials said ambassadorial-level contacts will remain open to assure a reliable channel of communication.
— The possible deployment and reinforcement of military assets in eastern NATO members, such as Poland and the Baltic states, that feel menaced by Moscow's latest actions.
— A possible increase of readiness levels for the NATO rapid response force.
— A possible review of NATO's crisis response plans, as well as its military training and exercise schedules.
NATO Supreme Commander Gen. Phil Breedlove and his subordinates will draw up the proposals within a few weeks and then submit them to political leaders for their approval, the NATO official said.
To reassure alliance members closest to Russia and Ukraine, NATO already has stepped up air patrols over the Baltic Sea and AWACS surveillance flights over Poland and Romania.
Prior to the meeting, the chief of the North Atlantic Treaty Organization downplayed reports of a Russian troop withdrawal from areas along its border with Ukraine. Russia's Defense Ministry on Monday said one battalion — about 500 troops — had pulled back.
"This is not what we have seen," NATO chief Anders Fogh Rasmussen told reporters Tuesday. "And this massive military buildup can in no way contribute to a de-escalation of the situation — a de-escalation that we all want to see — so I continue to urge Russia to pull back its troops, live up to its international obligation and engage in a constructive dialogue with Ukraine."
German Chancellor Angela Merkel, speaking to reporters in Berlin, echoed those comments.
"(Even if some troops left) it's certainly not the final step," she said. "The (Russian) troop concentration on the Ukrainian border is very high."
An estimated 35,000 to 40,000 Russian troops equipped with tanks, other armored vehicles and fixed and rotary wing aircraft remained positioned near the border with Ukraine, a NATO military official told The Associated Press on Tuesday, speaking on condition of anonymity because of the sensitive nature of the information.
The official described the Russian buildup as "a complete combat force" that was highly threatening to Ukraine.
Ukraine's foreign minister, who was meeting with his NATO counterparts, planned to speak to reporters later in the day.
In other developments, Russia sharply hiked the price for natural gas to Ukraine and threatened to reclaim billions in previous discounts, raising the heat on Ukraine's cash-strapped government. In Kiev, Ukrainian police moved to disarm members of a radical nationalist group after a shooting spree in the capital.
German Foreign Minister Frank-Walter Steinmeier renewed a push for internationally backed direct talks between Russia and Ukraine.