The scenarios at first sound hauntingly familiar: an American president preparing to attack a Middle Eastern country without a United Nations Security Council resolution, without broad international backing and, this time, not even with congressional support.

It's not the position that President Barack Obama ever hoped to find himself in during a presidency he said would be focused on nation-building at home. But mounting evidence that the regime of Syrian President Bashar al-Assad used chemical weapons – a violation of international law – against his own people appears to have changed the administration's calculus.

Obama has waffled on intervention for months, even after saying a year ago, in August 2012, that the use of chemical weapons in Syria would constitute crossing a "red line" that would force Washington's hand.

White House officials now say the U.S. is ready to pursue limited military strikes in Syria, even with a reluctant Congress at home, and a rebuke from the British Parliament Thursday, rejecting a call for military involvement.

In the Obama administration's maneuvers, some see echoes of the way in which President George W. Bush unilaterally, without a U.N. resolution and despite international critics, marched into war in Iraq in 2003 – a war that ended up costing thousands of American lives, thousands of Iraqi casualties and nearly $1 trillion.

The White House has understandably pushed back against those comparisons, as officials have tried to build support among allies abroad and Congress.

Secretary of State John Kerry said Friday that the U.S. had learned its lesson about the faulty intelligence that led to the Iraq War and in assessing the chemical weapons attack, Washington had been "more than mindful of the Iraq experience."

"We will not repeat that moment," Kerry said, adding, "Fatigue does not absolve us of our responsibility."