Aug 06, 2015 11:41 AM EDT By Russell Westerholm, UniversityHerald Reporter

The United States wants to end its reliance on Russia for ferrying astronauts to the International Space Station (ISS), but will have to hold off a while longer.

According to The Verge, NASA Administrator Charles Bolden penned a letter to Congress Wednesday revealing he had extended NASA's contract with the Russian Space Agency. Specifically, Bolden paid $490 million for six Soyuz spacecraft seats for NASA astronauts in 2018.

NASA is currently commissioning American commercial companies like SpaceX, Orbital Sciences, and Boeing to fly unmanned resupply missions to the ISS. However, these companies have yet to develop the technology to ferry astronauts to the low-orbit science laboratory.

That capability lies solely with the Russian Space Agency, and therefore the U.S. has been forced to pay hundreds of millions of dollars to save seats for its astronauts. SpaceX appears to be closest to developing an ISS taxi, but their first flight with humans aboard is tentatively slated for 2017.

"While I understand that funding is extremely limited," Bolden wrote in his letter, "it is critical that all of NASA's human spaceflight efforts be supported.

"It is my sincere hope that we all agree that the greatest nation on Earth should not be dependent on others to launch humans into space. I urge Congress to provide the funds requested for our Commercial Crew Program this year, so we can prevent this situation in the future."

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