US public opinion split as Republicans claim Obama's use of military force in Libya is 'an affront to our constitution'

Republican members of Congress are claiming the conflict in Libya is unconstitutional because Barack Obama failed to seek Congressional approval.

President Obama sent a letter defending the Libya intervention to members of Congress on Monday in an effort to quell a growing rebellion over his failure to consult the Senate and the House of Representatives before embarking on the third major military action of his presidency.

In the letter, Obama attempted to address criticism that he had failed to either brief or discuss his decision in detail with both Democrats and Republicans. Under the US constitution, Congressional approval is required for declarations of war.

Congressman Roscoe Bartlett, a Republican on the House armed services committee, was among members who argued that military action in Libya was unconstitutional. He told the Hill magazine: "The United States does not have a King's army. President Obama's unilateral choice to use US military force in Libya is an affront to our constitution."

The Libyan conflict appears to have crept up almost unawares on many members of Congress and the US public. Events moved at speed at a time when members of Congress were either in their home states or travelling back from Washington, with the vote at the United Nations on Thursday evening and bombing beginning two days later.

Obama contacted key members of Congress on Friday asking them either to attend a meeting at the White House or participate via phone. Some have since complained the line was bad while others said it was a briefing rather than a discussion.

The intervention in Libya has not yet generated much public debate, other than mild protests about becoming involved in another war and the cost at a time when budgets are being cut. Part of the reason is that so far there have been no US casualties and relatively few pictures of Libyan bodies shown on US television. There was also sympathy for the plight of the rebels threatened with massacre in Benghazi.

A survey by CNN/Opinion Poll conducted on Friday, Saturday and Sunday and published on Monday, recorded 50% approval for Obama's handling of the crisis, with 41% disapproving, and support for a no-fly zone climbing from 56% to 70% over the last week. There was overwhelming opposition to the use of US ground troops.

Ileana Ros-Lehtinen, a Republican who chairs the House foreign affairs committee, called on the president to "clearly define for the American people what vital United States security interests he believes are currently at stake in Libya".

The Republican House speaker, John Boehner, in a statement issued on Sunday, underlined the dilemma for Republicans. His statement was aimed primarily at criticising Obama for lack of consultation but he began by expressing support for intervention.

Republicans such as Senator John McCain have criticised Obama for acting too late, suggesting the forces would have been more effective if deployed weeks ago.

In his letter to members of Congress, the president detailed actions taken so far and his reasons for doing so, insisting it was a limited military operation done as part of a coalition.

Obama said: "For these purposes, I have directed these actions, which are in the national security and foreign policy interests of the United States, pursuant to my constitutional authority to conduct US foreign relations and as commander-in-chief and chief executive.

"I am providing this report as part of my efforts to keep the Congress fully informed, consistent with the War Powers Resolution. I appreciate the support of the Congress in this action."

Obama would have faced heavy criticism if he had stood by while a massacre took place in Benghazi, and criticism had been building from Republicans such as McCain about his lack of leadership.

Frank Luntz, the Republican pollster, told the Politico website: "It's a genuine test of foreign policy leadership. And this time, whatever happens can't be blamed on his predecessor. Short-term, his base voters won't be happy to see the US engaged in now a third conflict when they are strongly opposed to the other two. But in the long term, if this leads to Gaddafi being removed, he will score real political points among independents and swing voters. Basically, it's a high-risk, high-reward strategy."

Luntz added: "I can imagine the line that opens the presidential debate on foreign policy: 'Six presidents have talked about getting rid of Gaddafi. Six presidents talked. One president acted.'"