"This is a landmark day, one that recognizes the centrality of space to America's security and defence," Trump said on Thursday in a White House ceremony joined by John Raymond, the first commander of the Space Command.
"Those who wish to harm the US, to seek to challenge us on the ultimate high ground of space, it's going to be a whole different ballgame."
The Space Command will soon be followed by the establishment of the US Space Force as the sixth branch of the US Armed Forces, the President added.
Trump ordered the establishment of Space Command late last year, making it the 11th unified combatant command of the Department of Defence, Xinhua news agency reported.
After Trump's announcement, the White House said in a statement that the newly established Space Command is built to "protect America's dominance in space" by "employing assigned forces from every branch of the military" and "delivering combat power by operating superior space capabilities such as communications, intelligence, navigation, and early missile detection and warning".
The establishment of the Space Command represents a crucial step to improving the nation's space warfighting structure in the ever evolving world, the statement added.
A Space Command existed from 1985 to 2002, but was disbanded in the aftermath of the September 2001 terrorist attacks as the country focused on defence of the homeland.
The new command is believed to be a step towards building an independent Space Force, a plan that still requires Congress approval.
Ahead of the launch on Thursday, Secretary of Defense Mark Esper on Wednesday said: "As a unified combatant command, the United States Space Command is the next crucial step toward the creation of an independent Space Force as an additional armed service."
The US Defence Department officials had discussed Space Force legislation with the congress, sources told SpaceNews.
The Senate proposed a one-year transition before standing up a new military service but the House required no such transition, according to the sources.
The phased-in approach proposed by the Senate came out of concerns about excessive costs and growth in the military bureaucracy.
( With inputs from IANS )