He was speaking to the ISS from the White House during a special event
US President Donald Trump says he wants to see NASA reach Mars during his first term in office - or "at worst" during his second.
He was speaking to the International Space Station from the White House Oval Office to congratulate NASA Commander Peggy Whitson, for breaking the US record for the number of days in space.
Commander Whitson launched on November 17th, 2016, with 377 days in space already under her belt.
In 2008, Whitson became the first woman to command the space station, and on April 9th became the first woman to command it twice.
In addition, she holds the record for most spacewalks by a female astronaut.
NASA astronaut Jack Fischer, who arrived April 20th for his first mission, also participated in the call.
Thousands of students from across the US also watched the exchange.
Beginning the link-up, President Trump asked "Do you hear me?"
Commander Whitson answered: "Yes sir, we hear you loud and clear".
With astronaut Kate Rubins and daughter Ivanka Trump by his side, Mr Trump said: "Well that’s what we like: great American equipment that works".
"Today Commander Whitson, you have broken the record for the most total time spent in space by an American astronaut: 534 days and counting.
"That’s an incredible record to break – and on behalf of our nation and frankly on behalf of the world – I’d like to congratulate you."
Asked how she felt at breaking the record, Commander Whitson said it was "a huge honour" – adding "it’s an honour for me basically to be representing all the folks at NASA who make this spaceflight possible, and who make me setting this record feasible".
"We’re excited about the missions to Mars in the 2030s".
Astronaut Jack Fischer then outlined to President Trump the international effort involved in his launch to the Space Station: "I launched in a Russian vehicle with my Russian friend Fyodor Yurchikhin...the next day I install an experiment in the Japanese module that’s going to be looking at new drugs.
"A couple of hours later I watched our cremate Thomas Pesquet, a Frenchman, drive a Canadian robotic arm to capture a spaceship from Virginia carrying three and a half tonnes of cargo and science.
"The International Space Station is by far the best example of international cooperation and what we can do when we work together in the history of humanity".
President Trump then said: "What do you see a timing for actually sending humans to Mars?"
Commander Whitson replied: "I think as your bill directed it will be approximately in the 2030s” adding “Getting there will require some international cooperation to get it to be a planet-wide approach in order to make it successful".
Mr Trump said: "We want to try and do it during my first term or at worst during my second term – so we’ll have to speed that up a bit OK?"
Commander Whitson added: "We’ll do our best!"
The link-up commences at around 2.25: