The story revolves around a U.S. diplomat. At this future date, the world has two superpowers, the USA and Communist China. There is a dispute about how best to colonize Mars. The United States wants to terraform Mars. The Chinese want to genetically alter humans (explicitly referred to as “pantropy” in the story) so they can live on Mars as it is. The Europeans are floating a compromise of building pressure-dome settlements on Mars. Our protagonist has to come up with a solution.

One dated aspect of the story is that world population pressure is the motive behind colonizing Mars. But one prescient aspect of the story, in the background, is that the Soviet Union collapsed in the 1990s. In the timeline of the story, the USA and the USSR made joint Moon landings and other space projects in the 1990s but then the USSR collapsed.

The story was written no later than 1982, and probably in the 1970s.

Other than Walter Miller’s 1955 novella “The Darfsteller,” this is the only short story I remember reading postulating the collapse of the Soviet Union.

I searched under “China Mars pantropy,” “China pantropy,” and “China Mars.”