White House: US 'can act in Libya without Congress'
President Barack Obama does not need congressional approval for the US to continue its role in the Nato-led Libya mission, the White House has said.
In a 32-page document, the White House said the president already had legal authority to order forces into Libya.
A Vietnam War-era law states Congress must authorise participation in hostilities longer than 60 days.
Members of Congress have accused Mr Obama of violating that law since 20 May, when the 60-day deadline ended.
In the report delivered to Congress on Wednesday, the White House argues that US forces involved in the Nato campaign are merely playing a supporting role.
That role, the White House says, does not match the definition of "hostilities" as described under a 1973 law that constrains the US president's ability to wage military conflict.
"The president is of the view that the current US military operations in Libya are consistent with the War Powers Resolution and do not under that law require further congressional authorization," the White House wrote.
"US military operations are distinct from the kind of 'hostilities' contemplated by the resolution's 60-day termination provision," it added.
The US role in Libya involves helping Nato aircraft with refuelling operations and assisting with intelligence-gathering, the White House says.
The Obama administration insists that the US is not engaged in sustained fighting or "active exchanges of fire with hostile forces" that put US troops at risk.
Under the US constitution, the power to declare war lies with Congress.
If the president orders the US military into a conflict without an explicit declaration of war, the War Powers Resolution requires him to seek authorisation from Congress within 60 days or to end US involvement in the conflict.
The law allows the president to extend the period before going to congress for another 30 days.
Sunday marks 90 days since the US joined the Nato-led no-fly zone mission over Libya.
This week the Republican speaker of the House of Representatives, John Boehner, said "it would appear" that on that day the Obama administration would be in violation of the War Powers Resolution.
Mr Boehner said that the administration would be in breach of the resolution unless the White House "asks for and receives authorisation from Congress or withdraws all US troops and resources from the mission".
The White House rebuttal came as a bipartisan group of US lawmakers sued Mr Obama in federal court for taking military action in Libya without authorisation from Congress.
The lawsuit alleges that the president had violated the US constitution in bypassing Congress.
The lawsuit, which also targets Defence Secretary Robert Gates, challenges the policy "that any president can take the US to war unilaterally", Democratic Congressman Dennis Kucinich of Ohio said.
"We have asked the courts to move to protect the American people from the results of these illegal policies," he added.