The United States Thursday implicitly reserved the right to strike Syria, alone, in its own national interest, without waiting for allies to join an operation or for global approval.
The White House said President Barack Obama prized the United Nations and closely consulted allies, but that in the end, his first duty was to US national security, which he sees threatened by a Syrian chemical weapons attack.
"We certainly are interested in engaging with the global international community on this issue," said White House spokesman Josh Earnest.
"But at the same time, the president's chief accountability is to the American people that he was elected to protect.
"The president believes strongly in making the kinds of decisions and taking the kinds of steps that are necessary to protect our core national security interests that we've acknowledged are at stake in this situation."
The comments came as Britain, Washington's closest European ally struggles for a political consensus over Prime Minister David Cameron's plans to join expected US-led military action in Syria.
The political fracas in London has sparked speculation that a timetable for action, which many observers believe could see air strikes in Syria within days, could slip.
But at the State Department, spokeswoman Marie Harf said that "we make our own decisions in our own timeline," though styled international consultations on Syria as "incredibly important."
The Obama administration also hinted that unlike Britain, it did not see the need to wait for a report by UN inspectors in Syria on the chemical attack on a Damascus suburb on August 21.
"It's not within the mandate of those UN inspectors to assess the responsibility for the use of those weapons -- it's just within their mandate to assess whether or not they were used," Earnest said.
"That's no longer an open question."
On Wednesday, the Obama administration said that it did not see any future in a British bid to secure a mandate from the UN Security Council for attacking Syria, due to Russian opposition.
Administration officials have said that Obama sees perils for US national security in the belief that Syria shattered international norms by using chemical weapons, and that US interests and allies could be threatened.
"The Syrian regime's use of chemical weapons against their own people presents a situation where, yes, US national security interests are threatened," said Harf.
US officials are concerned that the Syria's chemical weapons stocks, as well as being used by civilians, could eventually fall into the hands of terror groups or radicals opposed to the United States.