"We have not done cost estimation yet", Shanahan told reporters at the Pentagon, adding that he expects he won't have a more concrete number until November.
Hours after Vice President Mike Pence outlined the Administration plans to create the Space Force - a proposed sixth military branch focused on space security- the Trump campaign sent out a mass email asking supporters to vote for a logo for the Space Force.
Establishing a new military service geared at space would be a massive undertaking and require action from Congress both to establish the service and provide funding.
"We need to address space as a developing war-fighting domain, and a combatant command is certainly one thing that we can establish", Secretary of Defense James Mattis said.
When the proposal for a separate force was launched previous year, Defense Secretary Jim Mattis resisted it. "In the realm of outer space, the United States Space Force will be that strength in the years ahead".
"This report is a step in a multi-year process that we think will result in a safer, stronger America", they said.
Mr Trump "knows that space is integral to our American way of life and economic prosperity and is a vital domain for national defence" while, under his direction, the U.S. is "reclaiming its heritage as the world's greatest space-faring nation", the White House said.
Several lawmakers have already hit back at the move as being costly and unnecessary.
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In the meantime, the Space Command would be led by a four-star general, and Pence said a new high-level civilian post - assistant defense secretary for space - would also be created.
The report also calls for the creation of "a Space Operations Force of career space experts who are trained, promoted and retained as space warfighting professionals" to include engineers, scientists, intelligence experts, operators and strategists. Only Congress has the authority to establish a new branch of the military-something that hasn't happened since the U.S. Air Force was founded in 1947. He said Beijing and Moscow have been developing missiles, lasers and other technologies with the aim of targeting USA satellites.
"The U.S. military is big in space, but it's all unmanned satellites", Brumfiel reports.
Currently, China and Russian Federation are America's primary rivals in space.
"To be clear: the Space Force will not be built from scratch, because the men and women who run and protect our nation's space programs today are already the best in the world", the vice president said.
THE GOAL. According to Pence, "It is not enough to have an American presence in space".
"Other nations are seeking to disrupt our space-based systems and challenge American supremacy in space as never before", the vice president said.
The Pentagon's existing military branches are: the Navy, Coast Guard, Marine Corps, Army and Air Force.