The 81-year old space grandee Armstrong criticised the fact that getting to the International Space Station (ISS) meant hitching a lift on decades-old technology, Russia's Soyuz, in order to make the journey,

"For a country that has invested so much for so long to achieve a leadership position in space exploration and exploitation, this condition is viewed by many as lamentably embarrassing and unacceptable," Armstrong said.

"A lead, however earnestly and expensively won, once lost, is nearly impossible to regain." He warned.

Armstrong's sentiments as the first human being to walk on the moon in 1969 were backed up a similar contribution from Eugene Cernan, 77, the last man to have stood on its surface in 1972.

"Today, we are on a path of decay. We are seeing the book close on five decades of accomplishment as the leader in human space exploration," said Cernan.