By Laura Smith-Spark, CNN

updated 5:21 AM EDT, Fri April 4, 2014

STORY HIGHLIGHTS

(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.

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NASA to end most activities with Russia