WASHINGTON (AFP) – President Barack Obama insisted that the current US military action in Libya was legal, rejecting rising criticism from Congress over the goals and justification of the operation.

In a 30-page report to lawmakers, the White House argued that US participation in the NATO-led assault on Moamer Kadhafi's forces did not require congressional authorization as the US role was only a supporting one.

The report said the US involvement in the UN-authorized operation did not rise to the kind of direct, offensive warfare that needed to be endorsed by lawmakers under the 1973 War Powers Resolution.

"US forces are playing a constrained and supporting role in a multinational coalition," the report said, noting that the use of force was being used solely to protect civilians, enforce a no-fly zone and an arms embargo.