BRUSSELS -- NATO is to hold an urgent meeting in Brussels to consider the situation in Ukraine.
The March 2 meeting of the North Atlantic Council, the alliance’s main political decision-making body, is at the request of Poland.
Warsaw has said it feels threatened by any potential Russian military intervention in neighboring Ukraine.
NATO Secretary-General Anders Fogh Rasmussen announced the meeting on March 1 on Twitter, saying: "Urgent need for de-escalation in Crimea."
“Russia must respect Ukraine's sovereignty, territorial integrity, & borders," he added.
A meeting of the NATO-Ukraine commission is to be held on March 3 in Brussels.
The NATO meetings come amid a flurry of Western diplomatic activity in response to the Ukranian crisis and fears Russia might intervene militarily.
Those fears rose on March 1 after Russia's upper house of parliament gave President Vladimir Putin approval to deploy troops to protect ethnic Russians in Ukraine and Russian naval forces based in the country's Crimea region.
Earlier, Ukraine's Defense Minister Ihor Tenyukh accused Russia of sending 6,000 troops and 30 armored personnel carriers into Ukraine's Crimea region since February 28 "without warning or Ukraine's permission."
British Foreign Minister William Hague will visit Kyiv on March 2.
He has called on Moscow to respect the independence of Ukraine in line with the 1994 Budapest Memorandum signed by Russia, the United States, and Britain.
The memorandum, agreed following the collapse of the Soviet Union, engaged all three powers to respect the independence, sovereignty, and territorial integrity of Ukraine.
Meanwhile, the U.S. White House says that President Barack Obama had a 90-minute phone call with Russian President Vladimir Putin on March 1.
Obama said the appropriate way for Russia to address any concerns in Ukraine "is peacefully through direct engagement" with the Ukrainian government and international mediating bodies.
The U.S. president also warned that continued violation of international law by Moscow would lead to further "political and economic isolation."
The Kremlin said Putin told Obama that Moscow will reserve its right to "protect its interests and Russian-speaking populations" in Ukraine.
Both the United States and Canada have suspended their engagements in preparations for the G-8 Summit, currently planned for Sochi.
U.S. Ambassador to the UN Samantha Power accused Russia of violating its international commitments.
Addressing an emergency session of the UN Security Council, she called for the "immediate deployment" of OSCE and UN observers to Ukraine to try to defuse the tensions there.
"It is time for the Russian intervention in Ukraine to end. The Russian military must stand down, the aspirations of the Ukrainian people must be respected, and political dialogue must be allowed to continue," Power said.
Ukrainian Ambassador to the UN Yuriy Sergeyev called on the Security Council to “do everything possible” to stop Russian "aggression."
UN Deputy Secretary General Jan Eliasson called for dialogue among all parties.
"It is important to recall the mission of this organization: to always search for peaceful settlement of dispute. This is the essence of the UN Charter and should serve as our primary guide in this situation. Now is the time for cool heads to prevail," Eliasson said.
EU foreign policy chief Catherine Ashton has urged Moscow to follow its international obligations to keep forces out of Ukraine and to promote its views through "peaceful means."
The European Union said EU foreign ministers will hold urgent talks over Ukraine on March 3.
With reporting by Reuters, dpa, AP, and AFP