US President Barack Obama tested a new prototype Tuesday for his commander-in-chief's arsenal -- a high-powered marshmallow gun that sent a tasty missile screaming through the White House.

Watched over by a brooding portrait of his hero Abraham Lincoln, the US president fired the launcher and marveled at other inventions on display at a White House youth Science Fair.

Obama gleefully examined a "Skype on wheels" robot that allows elderly people use the Internet to talk to far away relatives and a unique sugar sachet that dissolves in a cup of coffee, to avoid creating garbage. But he could not resist the marshmallow launcher.

"The Secret Service is going to be mad at me about this," Obama said, before energetically pumping a compressor and shooting the marshmallow gun, invented by 14-year-old Joe Huddy.

Obama watched open-mouthed as the candy shot across the room before crashing into the wall near the entrance to the Red Room, an elegant state parlor which stuffed with rare 19th century French furniture.

All the fun of the science fair had a serious purpose. Obama wanted to highlight the importance he places on innovation, science and education -- which will be reflected in his budget to be unveiled next week.

The president says that Republican budget cuts would dry up the kind of government spending that is necessary to inspire a new generation of scientists and visionaries to build a competitive 21st century economy.

"The young people I met today... you guys inspire me. It's young people like you that make me so confident that America's best days are still to come," he said.

"When you work and study and excel at what you doing in math and science, when you compete in something like this, you're not just trying to win a prize today; you're getting America in shape to win the future."

Obama said that the budget he unveils next week will include programs to prepare new math and science teachers and to qualify one million more US graduates in science, technology, engineering and math over 10 years.

He also had some advice for journalists and editors currently obsessing over campaign trail fireworks and his chances of winning a second term in November.

"I'm going to make a special plea to the press -- not just the folks who are here, but also your editors -- give this some attention," he said.

"I mean, this is the kind of stuff, what these young people are doing, that's going to make a bigger difference in the life of our country over the long term than just about anything."