Nasa has suspended most of its contact with Russia's space agency citing Moscow's "ongoing violation of Ukraine's sovereignty and territorial integrity" as the diplomatic stand-off between the two countries over the region continues unabated.
The suspension includes "travel to Russia and visits by Russian government representatives to Nasa facilities, bilateral meetings, email, and teleconferences or videoconferences," Michael F O'Brien, Nasa's associate administrator for international and interagency relations, wrote in an internal memo leaked on Wednesday.
Bilateral contact on the International Space Station, a joint space programme led by Nasa and Russia's Roskosmos space agency, will continue to operate as usual. Two US and three Russian astronauts are currently living together at the International Space Station (ISS).
In pictures: Ukraine crisis
In pictures: Ukraine crisis
1/12 Ukraine crisis
People shout slogans during a pro Russian rally at a central square in Donetsk. Pro Russian activists continued to gather on Saturday in the eastern Ukrainian city of Donetsk, as Russia was reported to be reinforcing its military presence in Crimea.
2/12 Ukraine crisis
In the same pro Russian rally, demonstrators show their support. Ukraine's ambassador to Russia and a deputy Russian foreign minister held a "cordial" meeting on Saturday, Moscow said, without giving details of any discussion of Russian-occupied Crimea.
3/12 Ukraine crisis
Crimean ethnic tatars stand on the roadside as Russian troops move towards to Simferopol in the settlement of Kok-Asan, some 70 kilometres from Simferopol in Crimea.
4/12 Ukraine crisis
Russian troops stand on a roadside in the settlement of Opytnoye, some 70 kilometres from Simferopol.
5/12 Ukraine crisis
Armed members of the first unit of a pro-Russian armed force, dubbed the "military forces of the autonomous republic of Crimea" march before the swearing-in ceremony in Simferopol, Ukraine. Some 30 men armed with automatic weapons and another 20 or so unarmed, were sworn in at a park in front of an eternal flame to those killed in World War II.
6/12 Ukraine crisis
A group of Cossacks march past a statue of Soviet revolutionary leader Vladimir Lenin in Simferopol as tensions in the area continue to rise.
7/12 Ukraine crisis
An armed member of the first unit of a pro-Russian armed force, dubbed the "military forces of the autonomous republic of Crimea" signs the oath during the swearing-in ceremony in Simferopol,
8/12 Ukraine crisis
9/12 Ukraine crisis
Ukrainian soldiers load their armed personnel carriers (APCs) into boxcars in the western Ukrainian city of Lviv. Pro-Kremlin militia fired warning shots as unarmed foreign observers tried to enter Crimea on the 8th.
10/12 Ukraine crisis
An abandoned naval ship sunk by the Russian navy to block the entrance is seen in the Crimean port of Yevpatorya on March 8th.
11/12 Ukraine crisis
Ukrainian sailors stand guard on top of the Ukrainian navy ship at the Crimean port of Yevpatorya.
12/12 Ukraine crisis
Crimea's pro-Moscow leader Sergei Aksyonov speaks to the media in Simferopol on the 8th March. He has defended a decision to hold a referendum on whether the region should join Russia, saying on Saturday that "no one" could cancel the voting.
Outspoken Russian deputy premier Dmitry Rogozin, who recently dismissed US sanctions on President Vladimir Putin's inner circle as a "prank", downplayed the seriousness of the suspension, insisting that Russian cooperation had always been limited to the ISS programme.
He tweeted:"Nasa has halted cooperation with Roskosmos, except for work on the ISS. But our cooperation with Nasa was only on ISS."
NASA suspends cooperation with Roscosmos (Rus Fed Space Agency) apart from work on the ISS (cont) http://t.co/h3rciFy9Cb— Dmitry Rogozin (@DRogozin) April 3, 2014
The partial suspension comes after Nasa insisted US- Russia space relations were fine despite tensions over Ukraine following the annexation of Crimea.
"Right now, everything is normal in our relationship with the Russians," Nasa Administrator Charles Bolden said during a Nasa budget teleconference.
Crimeans voted to leave Ukraine for the Russian Federation on 16 March following a controversial referendum condemned as illegal by Kiev and the West.
Prime Minister David Cameron dismissed the referendum as a "sham" echoing remarks made by President Barack Obama, who claimed "a sloppily organised (referendum) over the course of two weeks" would not be considered "a valid process".