Russian foreign minister warns west over ?aggressive line? in Ukraine crisis

Russia's top diplomat has warned the west that its "aggressive" approach to Ukraine and threat of sanctions could force Moscow to "eliminate unacceptable threats to our security", after a high-stakes conversation between Vladimir Putin and Joe Biden failed to deescalate the crisis.

The remarks by the Russian foreign minister, Sergei Lavrov, were published shortly after the Russian and US presidents held a 50-minute telephone call in which the two sides traded threats regarding tensions over Ukraine.

During the phone call, Biden told Putin that the US would impose serious sanctions on Moscow in the event that Russian forces, which include tanks, artillery and even short-range ballistic missiles, launched an attack on Ukrainian forces.

Yuri Ushakov, a Kremlin aide, said Putin responded that fresh sanctions could lead to a "complete breakdown in ties between our countries". "Our president also mentioned that it would be a mistake that our descendants would see as a huge error," Ushakov told reporters late on Thursday evening.

The US and other western countries have said Russia is massing military equipment on Ukraine's border for what could be a potential invasion force. Thousands of Ukrainian civilians have taken part in combat training in preparation for a potential Russian assault, although the situation in the country is largely normal ahead of the new year holiday.

Earlier this week, the secretary of Ukraine's national security council, Oleksiy Danilov, said Kyiv was concerned about Russian troops on the border but added that there was no panic. He said: "As for the troop buildup near our borders reported by foreign media - we do not see that. There is a certain increase of [Russian] military and we closely monitor what's happening at our borders."

Ukrainian military intelligence had previously warned of a massive buildup of Russian military equipment on the border and the potential of a large-scale Russian offensive by mid-January. Russian delegations are set to meet then with US, Nato, and Organisation for Security and Cooperation in Europe (OSCE) officials for a series of high-stakes talks on European security.