Ukraine was due to start two days of missile tests on Thursday – a move that has angered Russia, prompting it to put its air defense forces on high alert on the annexed Crimea& peninsula.
The disagreement marks a fresh escalation in tensions between the one-time allies, whose relations collapsed in 2014 after Russia seized& Crimea& and backed pro-Russian separatists fighting in eastern Ukraine.
Ukraine says the tests in its southern Kherson region, bordering& Crimea, are legitimate and will be conducted within the framework of international obligations and treaties.
Kremlin spokesman Dmitry Peskov told reporters on Wednesday that he did not know whether President Vladimir Putin had ordered the defense ministry to prepare a potential military response to the Ukrainian tests.
In September, Russia held large-scale war games across its entire southern military district, including& Crimea, which Ukraine and most of the international community say it illegally annexed in March 2014 after street protests toppled a pro-Moscow Ukrainian president.