Russia and the US disagree on the conditions of a potential New START nuclear treaty extension. The US demands that both nations freeze their nuclear warhead stocks between now and the treaty's expiration on February 5, 2021, but Russia refused this condition among others proposed by the US. The US was surprised that Russia rejected this proposal (initially assuming they'd accept), but both sides do see a potential deal as a victory for both sides, so it's fair to assume negotiations will continue.
