With a recent agreement between the US and India to collaborate on an unmanned Moon mission, and talks between the US (NASA) and China on the horizon, space and diplomacy are back as a means to stengthen/improve relationships with two emerging world powers. Just as in the days of the Cold War, where the US and USSR collaborated and had the in-flight rendezvous between Apollo and Soyuz spacecraft (1975) and the later and current collaboration between the US and Russia on the International Space Station, space missions are a way of showing, at the very least symbolically, some level of trust with each other as well as overall improving the relationsihp between two competing nations. There are practical reasons as well, including cost and the fact we have relied on Russian spacecraft to keep supplies going up to the ISS after the US shuttle fleet was grounded. Going into space is a scientific, technical, and economic challenge, and when missions are shared there exists added incentives to avoid confrontation politically as well as militarily.
Current foreign policy includes deepening our strategic alliance with India, the world's largest democracy, and there is an obvious need to improve and strengthen our relationship with an emerging superpower, China. While trade with China has constructed common interdependence between the US and China, including space policy and collaboration will be a second pathway between these competitors. And let's not forget that China is working on a mission that will make it the second nation to land men on the Moon; NASA is certainly interested in this one.