WASHINGTON - US House Speaker John Boehner told President Obama on Tuesday that the administration would be in violation of the 1973 War Powers Resolution this Sunday unless US Libyan operations end by then or Congress authorizes them.

In a letter to Obama, Boehner asked the president to explain the legal grounds for carrying out the Libya mission beyond Sunday, and asked for his reply by Friday.

"It would appear that in five days, the administration will be in violation of the War Powers Resolution unless it asks for and receives authorization from Congress or withdraws all US troops and resources from the mission (in Libya,) Boehner said in the letter, which was released by the Speaker's office.

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"Have you ... conducted the legal analysis to justify your position?" Boehner, a Republican, asked Obama, a Democrat. "Given the gravity of the constitutional and statutory questions involved, I request your answer by Friday, June 17, 2011."

The 1973 War Powers Resolution sought to set out the powers of the president and Congress regarding US military action. It was passed by Congress over the veto of President Nixon, but no sitting US president has recognized the act as binding.

The resolution prohibits US armed forces from being involved in military actions for over 60 days without congressional authorization, and includes a further 30-day withdrawal period.

Obama notified Congress in March that the United States was taking part in a multinational operation conducting air strikes to protect Libyan civilians from attacks by Muammar Gaddafi's forces. Obama did not ask for congressional authorization for the move.

NATO is leading the Libya intervention with a US contribution, but there are no US troops on the ground in Libya. The United States is providing NATO with logistical support and intelligence.

The White House says it has been consulting regularly with lawmakers on the war, and officials have suggested that the limited US action might not meet the War Powers threshold.

Earlier this month the House passed a resolution accusing Obama of not having offered a "compelling rationale" for the Libyan intervention, and demanding information about its costs and scope. Boehner's letter indicated lawmakers are still waiting for answers from the administration.