Mitt Romney lashed out at the Obama administration Wednesday as being weak on foreign policy after violent attacks on U.S. diplomatic missions in the Middle East in which four Americans were killed. President Barack Obama steered clear of the political fight, declaring as commander in chief that "justice will be done."

The GOP presidential hopeful used the attacks as an opening to assail Obama during an appearance in swing state Florida, accusing the administration of sending "mixed signals to the world" and failing to lead in the face of violence.

Obama avoided engaging his political rival during an appearance in the White House Rose Garden with Secretary of State Hillary Rodham Clinton. Addressing the nation and the world, he said there was "absolutely no justification for this kind of senseless violence — none." He was responding to the Tuesday night attack that killed U.S. ambassador to Libya Chris Stevens and three American members of his staff.

Romney had jumped to criticize Obama as the attacks were being waged on U.S. diplomatic missions in Egypt and Libya. the facilities to protest an obscure film by an obscure California filmmaker that ridiculed Islam's Prophet Muhammad.

The U.S. Embassy in Cairo initially issued a statement that criticized the film. Romney, trailing Obama in public opinion polls on their leadership on foreign policy, quickly sent out his own statement before news of the diplomats' deaths, saying the administration's statement seemed to "sympathize with those who waged the attacks." Romney incorrectly said the statement by the embassy in Cairo came "when our grounds are being attacked and being breached" — it actually was issued before the demonstrations planned in the neighborhood entered the compound and tore down the U.S. flag.

Romney advisers said it was difficult to follow the chronology of events in Libya late Tuesday — especially because he is not yet receiving the intelligence briefings that are customary relatively soon after a nominating convention. Republican officials say he has been relying on his foreign policy advisers and news reports.

But Romney advisers maintain he was correct in immediately condemning the violence against Americans — an effort to distinguish himself from the president's tone, which Romney calls apologist on some foreign policy matters.

As news of the deaths came from the White House Wednesday morning, the Romney team scrambled to change a speech before supporters in his Jacksonville, Fla., campaign headquarters to a more somber event. The supporters were ushered from the room and four flags were set up behind the podium from which Romney read a brief statement mentioning Egypt and contending that Obama is a weak leader. He then invited questions from reporters, who asked if it was an appropriate tone to take given the deaths and that the White House said it disagreed with the embassy statement. Romney stood firm.

"The president takes responsibility not just for the words that come from his mouth, but also for the words that come from his ambassadors, from his administration, from his embassies, from his State Department," Romney said. "They clearly sent mixed messages to the world. The statement that came from the administration — and the embassy is the administration — the statement that came from the administration was a statement which is akin to apology. And I think was a severe miscalculation."

Obama did not mention Romney and instead focused on the diplomats who were lost. He ignored reporters' shouted questions asking him to respond to Romney, keeping himself out of the fray and leaving the job to other Democrats.

"Governor Romney's comments are about as inappropriate as anything I have ever seen at this kind of a moment," Senate Foreign Relations Chairman John Kerry told reporters. "They are flat wrong but they demonstrate an insensitivity and a lack of judgment about what is happening right now. To make those kinds of statements before you even know the facts, before families have even been notified before things have played out is really not just inexperienced, it's irresponsible, it's callous, it's reckless. And I think he ought to apologize and I don't think he knows what he's talking about frankly."

The Mideast attacks pivoted the election to foreign policy, an area where the president who commanded the mission that killed al-Qaida leader Osama bin Laden has a lead in polling even though Republicans traditionally have an edge.

"The attacks in Libya and Egypt underscore that the world remains a dangerous place and that American leadership is still sorely needed," Romney said Wednesday. "In the face of this violence, American cannot shrink from the responsibility to lead. American leadership is necessary to ensure that events in the region don't spin out of control. We cannot hesitate to use our influence in the region to support those who share our values and our interests.

"As I've watched over the past three and a half years, the president has had some successes. He's had some failures," Romney said. "It's a hit-or-miss approach, but it has not been based upon sound foreign policy."

Obama was more cautious in responding to the attacks as the situation evolved. The White House says Obama was informed of the Libya attacks Tuesday afternoon during his weekly meeting with Pentagon leaders and told later in the evening that Stevens was unaccounted for. Obama learned of the ambassador's death Wednesday morning, the White House said.

On Capitol Hill, where flags were lowered to half-staff, Republicans mostly steered clear of the political criticism that Romney leveled at Obama over foreign policy, focusing on the lives lost in the Egyptian and Libyan attacks and imploring the two governments to condemn the incidents and protect American diplomatic missions.

Senate Republican Leader Mitch McConnell said Americans "will stand united in our response."

"Among the things we can all agree on in Washington is that attacks on the U.S. and its representatives will be met with resolve, and that America's presence and defense of our national interests across the globe will not be deterred by the acts of violent extremists," he said.