Washington - Nasa chief Charles Bolden said on Tuesday the US space agency's relationship with Russia remained normal despite the ongoing international crisis in Ukraine.
Russia is a key nation at the International Space Station, and US astronauts rely on Soyuz spacecraft to get to the orbiting outpost and back, having lost direct access since the US space shuttle fleet retired in 2011.
The US pays Russia some $70m to ferry each American astronaut to the space station and back, a deal that is expected to last for several more years until private US enterprises build the capacity to carry space travellers again.
Asked by reporters about the US space agency's ties with Russia during a media briefing that was announced to discuss US President Barack Obama's proposed fiscal year 2015 budget, Nasa administrator Bolden said nothing has changed.
"Right now, everything is normal in our relationship with the Russians," Bolden said.
"We continue to monitor the situation," he said, but stressed repeatedly that the US-Russian "partnership in space remains intact and normal".
Mike Hopkins, an American astronaut aboard the ISS, is set to return to Earth at the end of the month on a Russian rocket, and those plans have not changed, Bolden said.
"Things are nominal right now and our crews are doing well," he said.
Bolden said the US-Russian rapport in space goes back years, and recalled that it was not affected by the 2008 war between Russia and Georgia over break-away territories Abkhazia and South Ossetia.
"People lose track of the fact we have occupied the ISS now for 13 consecutive years uninterrupted and that has been through multiple international crises," Bolden said.
Earlier on Tuesday, the US government announced a $1bn support package for Ukraine as Secretary of State John Kerry visited Kiev.
Kerry accused Moscow of looking for a "pretext" to invade Ukraine and condemned Russia's intervention on the flashpoint Crimean peninsula as an "act of aggression".