Apollo 11 hero Neil Armstrong lashed out at President Barack Obama's decision to axe Nasa plans to return to the moon, describing the move as "devastating" to the US space programme.

Mr Armstrong, the first human to set foot on the lunar surface, was one of three former astronauts who signed an open letter to Mr Obama ahead of his visit to Florida where he will deliver a space policy speech.

Budget plans unveiled two months ago proposed scrapping the Constellation programme, which was developing a new rocket to take Americans back to the moon; and giving private industry the role of building the space vehicles to take humans to the International Space Station.

However, Mr Armstrong and fellow Apollo programme commanders James Lovell and Eugene Cernan bemoaned the proposals for the US space effort in a letter released to NBC News on Tuesday.

Mr Armstrong, Mr Lovell and Mr Cernan said that while some of Mr Obama's Nasa budget proposals had "merit," the decision to cancel the Constellation program, the Ares 1 and Ares V rockets and the Orion spacecraft, was "devastating".

American astronauts could now only reach low earth orbit and the ISS by hitching a ride on Russia's Soyuz spacecraft "at a price of over €50 million per seat," the letter said.

"For The US, the leading space faring nation for nearly half a century, to be without carriage to low earth orbit and with no human exploration capability to go beyond earth orbit for an indeterminate time into the future, destines our nation to become one of second or even third rate stature," the astronauts said.

"Without the skill and experience that actual spacecraft operation provides, the US is far too likely to be on a long downhill slide to mediocrity," they added in the letter.