The United States has concluded that Syria used chemical weapons against rebels, a U.S. official confirmed to ABC News.
President Obama and his administration had delayed making such a determination even though other countries had accused the regime of Syrian President Bashar al Assad of using sarin gas on rebel forces.
The use of chemical weapons has long been considered a "red line" by President Obama that could prompt more forceful action against the Syrian regime.
"Following a deliberative review, our intelligence community assesses that the Assad regime has used chemical weapons, including the nerve agent sarin, on a small scale against the opposition multiple times in the last year," Deputy National Security Advisor Ben Rhodes said.
"The use of chemical weapons violates international norms and crosses clear red lines that have existed within the international community for decades," he added.
Traces of chemical weapons were detected inside Syria months ago, but President Obama insisted on a thorough investigation by the intelligence community to determine who had used them.
It was unclear what new actions the United States might take. But some options might include more direct aid to rebel forces, which are bent on toppling the Assad regime, instituting a no-fly zone or even committing U.S. forces to Syria.
Rhodes said the president will expand non-lethal assistance to rebel forces. He will also "be consulting with Congress on these matters in the coming weeks."
The determination that Assad used chemical weapons won't necessarily lead to immediate U.S. intervention.
"The Obama administration will make decisions going forward on our own timeline," Rhodes told reporters.
Lawmakers from both parties have called on the Obama administration to do more regarding Syria.
Sen. John McCain, R-Ariz., who has been vocal on the need for more U.S. action against the Assad regime, praised the finding by the government and pressed Obama to offer "lethal assistance" to rebel forces.
"But providing arms alone is not sufficient," said McCain in a joint statement with Sen. Lindsey Graham, R-S.C. "That alone is not enough to change the military balance of power on the ground against Assad. The president must rally an international coalition to take military actions to degrade Assad's ability to use air power and ballistic missiles and to move and resupply his forces around the battlefield by air. This can be done, as we have said many times, using stand-off weapons such as cruise missiles.
"We cannot afford to delay any longer," the senators added. "Assad is on the offensive with every weapon in his arsenal and with the complete support of his foreign allies. We must take more decisive actions now to turn the tide of the conflict in Syria."
"Every bone in my body knows that simply providing weapons will not change the battlefield equation and we must change the battlefield equation," McCain later added on the Senate floor. "Otherwise, you are going to see a regional conflict the consequences of which we will be paying for a long, long time."
Sen. Saxby Chambliss, R-Ga., who sits on the Senate Intelligence Committee, said Thursday night he would support an American military operation against Syria.
"I have said for the last several weeks that doing nothing, [to] continue to do nothing, is not an option," said Chambliss, "We know now that almost 100,000 or maybe an excess of 100,000 people have been killed inside Syria – and the United States has sat by and watched that happen. We now know that the president said a red line was the use of chemical weapons. We know now that chemical weapons have been used for almost a year by the Syrian regime. We've done nothing. I think it's time that we act in a very serious way. If a no fly zone is what they've decided to do, I am sure our military is taking the right preparations for carrying out a successful operation. And I will support that."
The Office of the United Nations High Commissioner for Refugees issued updated casualty estimates on Thursday that identified 92,901 documented cases of individuals killed in Syria between March 2011 and the end of April 2013 and more than 5,000 killings documented every month since last July.
The UNHCR reported that there have been 27,000 new killings in Syria in 2013 and more than 6,000 children have been killed during the war.