(CNN) -- NASA is suspending much of its work with Russia in light of its actions in Ukraine but said it will continue to collaborate with Russia's space agency on International Space Station operations.
The decision by the U.S. space agency to halt "the majority of its ongoing engagements" with Russia's Roscosmos comes amid heightened tensions sparked by Russia's annexation last month of Ukraine's southern Crimea region.
A statement sent out by NASA on Wednesday said the U.S. space agency was acting "given Russia's ongoing violation of Ukraine's sovereignty and territorial integrity."
But, the statement said, it will continue to work with Roscosmos to "maintain safe and continuous operation of the International Space Station."
In 2011, NASA retired its space shuttle fleet, its only means of getting to and from the station. Now, Russian Soyuz capsules ferry U.S. astronauts and cosmonauts, together with supplies that can fit in the smaller craft.
In its statement, NASA appealed for more funding from Congress to help it resume manned American space flights.
"NASA is laser focused on a plan to return human spaceflight launches to American soil, and end our reliance on Russia to get into space," it said.
"This has been a top priority of the Obama Administration's for the past five years, and had our plan been fully funded, we would have returned American human spaceflight launches -- and the jobs they support -- back to the United States next year.
"With the reduced level of funding approved by Congress, we're now looking at launching from U.S. soil in 2017. The choice here is between fully funding the plan to bring space launches back to America or continuing to send millions of dollars to the Russians. It's that simple."
The U.S. space agency's decision to suspend many activities comes in the same week that 28-member defense bloc NATO said it was ending cooperation with Russia over its activities in Ukraine.
Western leaders have condemned Russia's annexation of Crimea as a violation of international law and called on Moscow to pull back the tens of thousands of troops it has massed near Ukraine's eastern border.
Russia says its forces are there to take part in military exercises and will return to base when those are finished.
CNN's Suzanne Presto contributed to this report.