A second phone call between Joe Biden and Vladimir Putin seemed not to achieve any "concrete outcomes" – yet both sides said the conversation was "productive", according to Spectrum News DC Reporter Austin Landis. It comes as the respective leaders of the United States and Russia held a 50 minute phone conversation – at the request of Mr Putin – which "set the tone" for further scheduled talks between the pair in January. Mr Biden raised concerns over the build-up of Russian troops on the Ukrainian border – and said the United States would not tolerate a Russian invasion. "President Biden said that he made it clear to Russia that they cannot invade Ukraine, that there will be serious consequences if they do, including sanctions," Ms Landis said. "Russia responded to that saying that sanctions would be a mistake – so still quite a lot of tension there."