BRUSSELS NATO allies will hold emergency talks on the crisis in Ukraine on Tuesday, for the second time in three days, following a request from Poland, the alliance said on Monday.
In calling the meeting, Poland, a neighbor of Ukraine, invoked a NATO rule allowing any ally to consult with the others if it feels its security, territorial integrity or independence are under threat, the so-called Article 4.
"The developments in and around Ukraine are seen to constitute a threat to neighboring Allied countries and having direct and serious implications for the security and stability of the Euro-Atlantic area," the alliance said in a statement.
NATO meetings under Article 4 are rare. Only Turkey has used the option before, calling for consultations three times, once during the 2003 war in Iraq and twice, two years ago, over the Syrian conflict.
In Sunday's discussions, the NATO allies urged Russia to withdraw its troops back to their bases but failed to agree any significant steps to rein it in.
Russian President Vladimir Putin's forces tightened their grip on the mostly Russian-speaking Crimea region on Monday after seizing the Ukrainian peninsula, and Putin has secured parliamentary approval to send other forces to Ukraine.
Poland has taken a more aggressive stance against Russia than some of its European peers, pushing for more decisive response, including possible European Union sanctions.
It has a special interest in Ukraine. They share a border, their languages are similar, and large parts of western Ukraine were Polish before World War Two. Polish foreign policy is driven by a fear of Russia, its former overlord, pushing west into Ukraine.
NATO also requested a meeting with Russia on Wednesday and Moscow's ambassador to the alliance, Alexander Grushko, said he would consider the proposal, the alliance said.