U.S, Obama To Complete Investigation Before Attacking Syria

The United Nations argued Sunday for world leaders to wait until its probe is completed into whether chemical weapons were used.

"The U.N. mission is uniquely capable of establishing in an impartial and credible manner the facts of any use of chemical weapons," Martin Nesirky, spokesman for Secretary-General Ban Ki-moon, said repeatedly at a news conference.

While member states are encouraged to share any relevant information, Nesirky said he didn't know whether the United States had shared the information Kerry referred to.

The U.N. is giving no timeline as to when results will be ready, Nesirky said. "It's being done as fast as it is possible to do within the scientific constraints."

Samples will be delivered to laboratories Monday, he said.

The investigation involves a strict chain of custody and clear guidelines, he said, adding that two Syrian government officials monitored the process.

But even when it's done, the U.N. will only say whether chemical weapons were used -- not who was responsible.

Obama changes course

U.S. military action appeared imminent until Saturday, when Obama announced he would first seek Congress' approval.

Lawmakers come back from recess September 9.

Obama's last-minute decision

The president's decision quickly drew criticism from those who support and those who oppose a strike.

"We can't understand how you can promise to help those who are being slaughtered every day in the hundreds, giving them false hope, then change your mind and say let's wait and see," said the Syrian National Coalition, a key group of Syrian dissidents.

Iran, a staunch supporter of the Syrian regime, warned the United States will pay a price if it strikes Syria.

Even the slightest attack by the United States against Syria will result in dire consequences, Iranian Brig. Gen. Mohammad Reza Naqdi said, according to the state-run FARS news outlet. The agency did not specify what those consequences would be.

Sarin allegedly used previously in Syrian civil war

World leaders have said previously that sarin has been used in the Syrian civil war.

In April, the United States said it had evidence sarin was used in Syria on a small scale.

In May, a U.N. official said there were strong suspicions that rebel forces used the deadly nerve agent.

In June, France said sarin had been used several times in the war, including at least once by the Syrian regime.

Fast Facts: sarin gas

Dr. Sanjay Gupta: How 'gruesome' sarin gas can kill

U.S. lawmakers are deeply divided on what the United States should do after the purported chemical weapons attack on civilians August 21, which killed hundreds of people in rebel strongholds.

On Saturday, Obama said "well over 1,000 people were murdered." Kerry on Friday cited a death toll of 1,429, more than 400 of them children.

Obama's last-minute Syria switch

After signaling he was on the verge of delivering a strike against Syria, Obama made a last-minute decision Friday evening to seek congressional authorization before any military action, senior administration officials told reporters Saturday.

"While I believe I have the authority to carry out this military action without specific congressional authorization, I know that the country will be stronger if we take this course, and our actions will be even more effective," Obama said Saturday. The 1973 War Powers Act technically allows him to strike without such approval.

U.S. authorities are tightening domestic security measures. The FBI and the Department of Homeland Security are warning of a higher risk of cyberattacks after months of disruptions by hackers known as the Syrian Electronic Army, and authorities say more attacks are likely.

Britain has voted against taking any military action in Syria, and France said it won't act without the United States as a partner.

"France cannot act alone," Interior Minister Manuel Valls told Europe Radio 1 on Sunday. "There must be a coalition."

France's prime minister will meet with government ministers and other officials Monday to discuss Syria, two days before an open debate on Wednesday, the French government said.

German Foreign Minister Guido Westerwelle tweeted Sunday that the time gained waiting for U.S. congressional approval "must be used to reach a common position of the international community within the U.N. Security Council."

In another tweet, Westerwelle said the results from a U.N. inspectors' visit to Syria "must be sped up."