US astronaut Buzz Aldrin speaks during a press conference in Hong Kong. NASA should focus on sending a man to Mars and helping other nations travel in space, Aldrin said.

Aldrin, who was the second man to set foot on the moon after Neil Armstrong, said the US space agency needed to stop concentrating on simply developing new rockets and turn its attention to visiting the neighbouring planet.

"I think our resources should... be on a pathway that can lead us to Mars," he told reporters during a trip to Hong Kong.

Aldrin added that when the Apollo 11 crew returned from their mission and began touring the world, they realised the sense of achievement did not belong only to them.

"We spoke to many people in different countries and they said, 'We did it'," said Aldrin. "These quests to space are capable of unifying people to see the successes of the human race."

"I think the moon needs to be visited by nations with space programmes that have not realised that point yet," he said. "[The US] can help them do that, with our experience."

Aldrin was speaking at the launch of a three-day exhibition at the Hong Kong Space Museum celebrating the moon landing. The 40th anniversary of the landing falls on July 21.

The 79-year-old recently opened an account on the social networking site Twitter to promote the 40th anniversary. He currently has more than 3,000 followers.

When asked what he would have tweeted to the world after walking on the moon, Aldrin smiled and said, "I can't wait to get home."