For the first time in six years, NATO on Wednesday invited a new member to join the military alliance, prompting a heated response from Russia and further underscoring escalating tensions between the Cold War adversaries.<br />The invitation, to tiny Montenegro, came nine years after the Balkan nation began the process of accession.<br />But the timing of the offer came at a particularly delicate moment as the West is trying to persuade Russia to link forces to help defeat the Islamic State and end the civil war in Syria.<br />In Moscow, the offer to Montenegro which has a population of about 600,000 and little military capacity prompted fury and threats.<br />Dmitri S. Peskov, the Kremlin spokesman, said that a NATO expansion would be met with unspecified retaliatory measures from Russia.
