Washington (CNN) -- President Barack Obama is returning home to a firestorm of criticism over his handling of the crisis in Libya and mounting calls for a clearer explanation of U.S. policy in the war-torn North African nation.
The president, who just wrapped up a five-day trip to Latin America, has insisted that the goal of the U.N.-sanctioned military mission is strictly to prevent a humanitarian crisis. Specifically, the mission is meant to prevent a slaughter of Libyan rebels and other civilians by forces loyal to strongman Moammar Gadhafi.
Obama, however, has also said the administration's ultimate objective is Gadhafi's removal from power. U.S. officials have indicated they hope the dictator will be removed quickly by forces currently loyal to him, though they haven't publicly called for a coup.
"Gadhafi has a decision to make and the people around him each have decisions to make," Secretary of State Hillary Clinton said Wednesday. "We would certainly encourage that they make the right decision."
Critics on Capitol Hill and elsewhere are angry over what they consider inadequate administration consultation with Congress before the start of the military mission over the weekend. They also continue to have questions over the conflict's cost and consequences as well as the U.S. endgame.
Obama himself conceded in an interview with CNN Tuesday that Gadhafi could "hunker down and wait it out even in the face of (the U.N.) no-fly zone, even though his forces have been degraded."
House Speaker John Boehner, R-Ohio, sent a letter to Obama on Wednesday complaining that "military resources were committed to war without clearly defining for the American people, the Congress, and our troops what the mission in Libya is and what America's role is in achieving that mission."
"In fact," Boehner said, "the limited, sometimes contradictory, case made to the American people by members of your administration has left some fundamental questions about our engagement unanswered."
Among other things, Boehner asked whether it is acceptable for Gadhafi to remain in power once the military campaign ends.
"If not, how will he be removed from power?" Boehner asked. "Why would the U.S. commit American resources to enforcing a U.N. resolution that is inconsistent with our stated policy goals and national interests?"
Boehner also asked Obama that since the "stated U.S. policy goal is removing Qadhafi from power, do you have an engagement strategy for the opposition forces? If the strife in Libya becomes a protracted conflict, what are your administration's objectives for engaging with opposition forces, and what standards must a new regime meet to be recognized by our government?"
Another key House Republican called for a withdrawal of U.S. forces Wednesday, arguing that Obama had failed to rally public support for military action.
"Mr. President, you have failed to state a clear and convincing explanation of the vital national interest at stake which demands our intervention in Libya," said Representative Candice Miller, R-Michigan. "You have failed to state a clearly defined mission for our military to defend that interest. ... I believe you must pull our forces from the coalition immediately."
California Republican Rep. Tom McClintock sent his own letter to Obama on Wednesday, contending the president violated the War Powers Act and other constitutional restrictions against authorizing military action.
"With all due respect, I can only conclude that your order to United States Armed Forces to attack the nation of Libya on March 19, 2011 is in direct violation of the War Powers Resolution and constitutes a usurpation of constitutional powers clearly and solely vested in the United States Congress and is accordingly unlawful and unconstitutional," McClintock's letter said.
Liberal Democrats have also expressed unease with the Libyan intervention, particularly in regard to the relative lack of congressional consultation and the prospects for an open-ended conflict.
Arizona Representative Raul Grijalva and California representatives Barbara Lee, Mike Honda and Lynn Woolsey released a statement late Tuesday arguing that "the United States must immediately shift to end the bombing in Libya."
"We will fight in Congress to ensure the United States does not become embroiled in yet another destabilizing military quagmire in Libya with no clear exit plan or diplomatic strategy for peace," they said.
Top Senate Democrats, however, continue to defend the administration, insisting that Obama moved methodically and carefully to assemble a strong international coalition capable of saving innocent lives and reinforcing the broader Middle East reform movement.
Senator Richard Durbin, D-Illinois, told reporters Wednesday that Obama's pursuit of international approval was reminiscent of former President George H.W. Bush lining up global support before taking military action to drive Iraq from Kuwait in the early 1990s.
Obama has pursued a "very prudent course of action," Durbin said. The United States is supporting "unprecedented and long overdue change" that is consistent "with our national values."
Durbin noted that, if the conflict drags on, members of Congress could push for a vote of approval under the 1973 War Powers Act.
We are "coming to the support and to the aid of a democratic movement in general and trying to protect a population inside Libya to the extent that it is possible," said Michigan Senator Carl Levin, chairman of the Senate Armed Services Committee.
If the president hadn't taken the time to assemble a broad coalition in Libya, there would have been "huge opposition ... in the streets of the Arab world," Levin said. Protests currently aimed at Arab dictators "would have been turned against us."
Senator Jack Reed, D-Rhode Island, stressed the administration's intention to hand over leadership of the military effort to international allies as soon as possible.
U.S. operations have generally been limited to America's "unique capabilities" relating to the establishment of a no-fly zone, he said.
Some analysts, however, echoed complaints about what they insisted was unclear administration guidance about ultimate U.S. goals in Libya and the methods being used in pursuit of those objectives.
Obama has been "fairly muddy in what he's said," argued Max Boot, a senior fellow at the Council on Foreign Relations. The president has been "reacting frantically" to events and "being pulled hither and yon."
Boot predicted air power would not be sufficient to knock out the Gadhafi regime and warned of a "protracted and costly stalemate," if the United States doesn't send in military advisers to help arm and train the rebels.
Obama may be hoping for a palace coup, Boot said, but "I wouldn't bet on it."
Boot also stressed the need for more planning for a post-Gadhafi Libya. There's a "real danger of chaos" and protracted tribal warfare, if Gadhafi falls, he said. Al Qaeda may be able to exploit such a situation, he warned.
Boot blasted the White House for "not really preparing the American people for the possibility that this could be a protracted and expensive conflict."
"The public and the administration should not be going into this with rose-colored blinkers on," he said.
But Thomas Mann, a senior fellow at the Brookings Institute, told CNN that Obama "has no interest in a full-scale war with Libya and every intention in keeping our mission there limited in scope and duration."
Mann also argued that Obama "probably doesn't want a congressional vote of approval because it would heighten the public attention and the stakes involved."
Still, "while Congress has no stomach for assuming responsibility for approving or reversing the steps taken by Obama, the president (would be) well advised to step up his consultation with the first branch of government," he said.
Wendy Schiller, a Brown University political scientist, argued Obama may have eventually paid a political price, if he didn't intervene before Gadhafi's troops took control of the last rebel stronghold in Benghazi.
"Americans generally do not like to see protesters seeking political rights shot, wounded or killed," she said. "Standing by and watching that happen, especially after the U.N. authorized a no-fly zone, would have made Obama look weak and indifferent to their struggle."
CNN's Deirdre Walsh contributed to this report