U.S. space agency NASA said Wednesday that it has suspended the majority of its engagements with Russia due to the Ukraine crisis. NASA and its Russian counterpart Roscosmos, however, will continue to work together to maintain safe and continuous operation of the International Space Station (ISS), the space agency said in a statement emailed to Xinhua. There are currently three Russians, two Americans and one Japanese aboard the ISS. Earlier, an internal letter published by the U.S. space news website Spaceref said that the U.S. government has determined that all NASA contacts with Russian government representatives are suspended, "unless the activity has been specifically excepted." "This suspension includes NASA travel to Russia and visits by Russian government representatives to NASA facilities, bilateral meetings, email, and teleconferences or videoconferences. At the present time, only operational International Space Station activities have been excepted," the letter said. In addition, multilateral meetings held outside Russia that may include Russian participation are not precluded under the present guidance, it added. In March, NASA Administrator Charles Bolden repeatedly said that space cooperation between the two countries would not be affected by tensions over Ukraine. "Right now everything is normal in our relationship with the Russians," Bolden said on March 4. "Since the International Space Station has been in orbit, it's very important to understand that started a partnership between the United States and Russia. That partnership remains intact and normal." NASA is currently totally dependent on Russian spacecraft to ferry astronauts to the ISS and back after retiring the Space Shuttle in 2011, and it hopes to change this within the next four years by using commercial spacecraft currently under development.