President Mahmoud Ahmadinejad has said he is ready to take the risk of becoming the first human being sent into space by Iran, national media reports.

"I'm ready to be the first Iranian to sacrifice myself for our country's scientists," the official IRNA news agency quoted him as saying on the sidelines of an exhibition of space achievements in Tehran on Monday.

Iran said it sent a monkey into space one week ago, describing the launch as a successful step towards Tehran's plan to send an astronaut into space within the next five to six years. The monkey named "Pishgam", which means pioneer in Farsi, reportedly travelled 120km and safely returned to Earth.

The launch added to Western concerns about Iran's space programme because the same rocket technology could potentially be used to deliver a nuclear warhead on a ballistic missile.

In 2010, Iran said it launched an Explorer rocket into space carrying a mouse, a turtle and worms.

Iran's space officials say Iran will launch a bigger rocket carrying a larger animal to obtain greater safety assurances before sending a man into space.

Space tourist Anousheh Ansari was the first Iranian to make a journey into space aboard a Soyuz TMA-9 capsule from Baikonur, Kazakhstan, in 2006. The 40-year-old telecommunications entrepreneur paid a reported $20m for a space station visit.

McCain's joke

Reacting to Ahmadinejad's space ambitions, Republican US Senator John McCain posted on his Twitter account: "So Ahmadinejad wants to be first Iranian in space - wasn't he just there last week?"

The tweet caused a stir online, with some of his nearly 1.8 million followers positing angry responses.

"Wow, way to elevate political discourse," tweeted @heyitsurban to McCain.

Another user, @manolo_loop, wrote: "@SenJohnMcCain is racism funny?"

Less than an hour after his first post, McCain sent another tweet, saying: "Re: Iran space tweet - lighten up folks, can't everyone take a joke?"

Questions were raised about last week's monkey mission after it turned out one of two official sets of photos of the famed simian space traveller depicted the wrong monkey.

The two different monkeys shown caused some international observers to wonder whether the monkey had died in space or that the launch did not go well.

One set of pictures showed a relatively dark-haired monkey. Another showed a different monkey - strapped in a pod - that had light grey hair and a distinctive red mole over its right eye.

A senior Iranian space official said one set of pictures had been released by mistake, showing an archive photo an alternate monkey not selected for the mission.