Russia wants to build a replacement for the Space Station, but NASA is looking to Mars

The head of Russia’s Roscosmos space agency dropped a bit of a bombshell on the space world, claiming that it is working with NASA on a replacement for the International Space Station. But today, NASA released a statement that effectively said, "We’re not sure what you’re talking about."
"Roscosmos and NASA will fulfil the program of building a future orbital station," Igor Komarov is quoted as saying. "We will elaborate the details. It is going to be an open project, not restricted only to current participants, but open for other countries willing to join it." This is quite a surprise, given that Russia had recently been talking about going its own way after the ISS’ life span runs out in 2024. The "open for other countries" is also contrary to US policy, which prevents NASA from cooperating with China in space exploration.
But today, NASA released a statement to NBC News that basically ignored the space station issue. "We are pleased Roscosmos… expressed interest in continuing international cooperation for human space exploration," NASA told the site. The agency instead focused on its plan to go to Mars: "The United States is planning to lead a human mission to Mars in the 2030s, and we have advanced that effort farther than at any point in NASA’s history."
In any case, having Russia commit to keeping the ISS in operation until the planned end of its lifespan in 2024 allows NASA to plan experiments to test the effects of extended stays in space, a necessity for any Mars mission. If all goes according to plan, however, by the time 2024 is here, NASA should have commercial taxi services to low Earth orbit, as well as an Orion-based exploration program in progress. It would make sense for NASA to evaluate whether a space station presence is appropriate under those changed circumstances.