Kelly, who has a twin brother Mark, told Baldwin "this idea seems to have come from one person who is not a space or military expert" - President Trump - and "a longer discussion" was needed on the issue.
President Donald Trump's administration on Thursday outlined an aggressive plan for creating a sixth branch of the USA military by 2020 - a Space Force to better confront emerging security threats - but the proposal will need approval from a divided Congress.
"The Space Force is the next and natural evolution of American military strength".
In a letter to a USA congressman, he said he did "not wish to add a separate service that would likely present a narrower and even parochial approach to space operations", adding it would create extra bureaucracy and cost.
The report, Pence said, recommends four actions: Establishing a unified combatant command for space operations led by four-star general or admiral; creating, "An elite group of joint warfighters specializing in the domain of space, who will form the backbone of the nation's newest armed service;" standing up the Space Development Agency to develop new technologies; and naming a civilian leader who reports to the defense secretary, who will oversee the growth of Space Force. Both nations are reportedly developing "hypersonic missiles", which US missile defense radars may not be able to detect.
Mattis past year opposed a House effort to establish a space corps within the Air Force, even sending a letter Congress stating his position.
In March this year, Mr Trump's National Space Strategy was said to recognise U.S. "competitors and adversaries have turned space into a warfighting domain".
Actions by USA adversaries make it clear that space is already a warfighting domain, the vice president said.
Several lawmakers have already hit back at the move as being costly and unnecessary.More news: Paul Pogba wants out of Manchester United as deadline day drama looms
They said the Pentagon report was the start of a "multi-year process that we think will result in a safer, stronger America".
Defense Secretary Jim Mattis has endorsed steps to reorganize the military's space warfighting forces and create a new command, but has previously opposed launching a pricey, new service.
Joan Johnson-Freese, a space security expert at the Naval War College, told Brumfiel that she doesn't think a Space Force is now necessary.
Social media users have been quick to mock the idea of a new military branch.
Rather than building up a Space Force from scratch, the Pentagon will take individuals and units working on space programs in the Air Force and other branches, with the objective of having the "United States Department of the Space Force" by 2020.
"As President Trump has said, in his words, it is not enough to merely have an American presence in space - we must have American dominance in space", Pence said. He said Beijing and Moscow have been developing missiles, lasers and other technologies with the aim of targeting United States satellites.
In every domain, America will always seek peace, the vice president said.
Trump, the champion of the plan, tweeted: "Space Force all the way!".
The Pentagon's existing military branches are: the Navy, Coast Guard, Marine Corps, Army and Air Force. We are in complete alignment with the president's concern about protecting our assets in space that contribute to our security, to our economy.