"I urge Russia to take the path of diplomacy. We are ready to talk," Truss will say, according to extracts of her speech released by her office.
"But we are very clear – if they decide to continue down the path of aggression, there will be massive consequences, bringing Russia severe economic costs and pariah status." Britain's foreign ministry did not give details of when the trip would happen.
Russia said this week that its forces - part of a huge buildup that has been accompanied by demands to the West for sweeping security guarantees - were pulling back after taking part in exercises in southern and western military districts near Ukraine.