NASA Deputy Administrator Dava Newman attends ceremonies in memory of the crews of Apollo 1 and the space shuttles Challenger and Columbia on Thursday, at Arlington National Cemetery in Arlington, Virginia. [Photo/Agencies]

The United States marked the 30th anniversary on Thursday of the explosion of the space shuttle Challenger with a pledge to remember lost astronauts as it presses on toward Mars.

At the Kennedy Space Center in Florida, where the shuttle blasted off on January 28, 1986, singers in red and blue belted out the Star Spangled Banner for a crowd that included relatives and friends of the seven killed that day.

Six NASA astronauts and Christa McAuliffe — who would have been the first teacher in space — died when the shuttle exploded 73 seconds after liftoff.

The cause was a failed booster engine, according to the US space agency.

"These brave women and men are forever a part of a story that is ongoing," President Barack Obama said in a statement.

Wreaths were laid at Arlington National Cemetery near the US capitol as NASA commemorated the 24 US lives lost in space disasters and test flights over the years.

"As we undertake a journey to Mars, they will be with us. They have our eternal respect, love and gratitude," former astronaut and NASA administrator Charles Bolden said in a statement.

The other major shuttle accident was on February 1, 2003. Seven people died aboard the space shuttle Columbia when it broke apart on re-entering Earth's atmosphere.

NASA said later that a piece of foam had come loose from the external tank during launch and punched a hole in one of the shuttle's wings, causing it to break up 16 minutes before it was to have landed.

The US space agency also commemorated the three men who died in the Apollo 1 launchpad fire in 1967.