To the long list of ambitious goals he has set, no matter how far-fetched they might seem, President Donald Trump on Monday added this: placing humans on Mars.

In a dramatic call from the White House with a pair of astronauts at the International Space Station, Trump urged NASA to speed up its exploration timeline to get humans on Mars "at worst, during my second term."

Trump was celebrating Commander Peggy Whitson, an astronaut who set a new U.S. record of cumulative days in space at more than 534 days. Trump spoke live on a video conference call for about 20 minutes from the Oval Office with Whitson and a second astronaut, Flight Engineer Jack Fischer, who also was at the space station. The president marveled at the sophisticated technology that allowed them to have a relatively clear conversation.

"That's what we like, great American equipment that works," said Trump, who sat at his desk and was flanked by his daughter, Ivanka, and astronaut Kate Rubins. A number of advisers, including Education Secretary Betsy DeVos, also were in the Oval Office during the call.

The conversation was streamed in classrooms across the country, in part to encourage girls to study science, technology and math.

"I've been dealing with politicians so much - I'm so much more impressed with these people, you have no idea," Trump said of the astronauts.

At one point, the astronauts explained that they recycle their urine into water, to which the president, a noted germaphobe, quipped, "Better you than me."

Trump noted that he has "many friends" involved in commercial space exploration. "Many American entrepreneurs are racing into space," Trump said.

Two prominent businessmen - Tesla founder Elon Musk and Amazon founder Jeff Bezos, who also owns The Washington Post - have companies, Space X and Blue Origin respectively, at the forefront of commercial space activities. Musk has said he wants to launch the first humans to Mars in 2024.

During his call with the astronauts, landing humans on the surface of Mars seemed to be top-of-mind for Trump.

"Who's ready to go to Mars up there?" Trump asked Whitson and Fischer.

Slide to the 30-minute mark for the video of the Trump call with astronauts: