Star Trek: Into Darkness has warped its way to a $US70.6 million opening weekend launch in the United States.

But the film is not setting any light-speed records with a debut that's lower than the studio's expectations.

The latest voyage of the starship Enterprise fell short of its predecessor, 2009's Star Trek, which opened with $US75.2 million.

Since premiering Wednesday in huge-screen IMAX theaters and expanding Thursday to general cinemas, Into Darkness has pulled in $US84.1 million, well below distributor Paramount's initial forecast of $US100 million. The film has added $US80.5 million overseas.

The Star Trek sequel bumped Iron Man 3 down to second-place after two weekends on top. Robert Downey Jr.'s superhero saga took in $US35.2 million domestically and $US40.2 million overseas, shooting its worldwide total to nearly $US1.1 billion.

Originally published as Trek warps to $70m debut weekend