He repeated his criticisms of the current direction of the US human spaceflight programme, saying it lacked ambition compared with the big thinking of the 1960s.

BBC: Neil Armstrong: 'Diffident' emissary of mankind

The White House's chief scientist, John Holdren, said "it would be only prudent" to review the human spaceflight programme given the scale of its ambition and "the significant investment of both funds and scientific capital".

BBC: Obama reviews post-shuttle plans

Human spaceflight is an optional programme for Esa member states, and so far the UK has declined to invest in it.

BBC: 'UK spaceman' Nicholas Patrick honoured

This week, a panel convened by the White House to review human spaceflight plans said the rocket programme was not viable under the US space agency's present funding.

BBC: Test ignition for 'Moon rocket'

ALH84001 hit the headlines, the space-science programme's funding seemed vulnerable to the insatiable demands of manned spaceflight.

ECONOMIST: Nice picture. Where to next?

Spaceflight, to quote the old cliche, is hard, and at some point the Chinese programme will encounter problems.

BBC: China in space: Running fast to catch up

"The budget is going to be an extremely challenging topic, not only for this programme but for all Nasa programmes, " said Phil McAlister, the agency's commercial spaceflight development director.

BBC: US firms target astronaut flights