The United States is preparing for talks with Russia that could start within weeks, a senior official said as Western powers accuse Moscow of continuing a major troop build-up on the border with Ukraine.

“The US is ready to engage in diplomacy as soon as early January,” both bilaterally and through “multiple channels,” the US official said. “There are some issues that Russia has raised that we believe we can discuss, and others that they know very well we will never agree to.”