A United Nations inspection team braved sniper fire to collect evidence and interview survivors, witnesses and doctors in its probe of an alleged chemical attack, according to UN Secretary-General Ban Ki-moon.

A vehicle carrying the scientists was hit by fire from a sniper en route to the Damascus suburb where Syrian rebels allege that chemical weapons killed more than 1,300 people, Ban said in an e-mail. After returning to Syria’s capital for a new vehicle, the team reached the site, visited two hospitals, conducted interviews and gathered samples, Ban said.

While the UN investigated, world leaders from Washington to Istanbul called for action to punish Syrian President Bashar al-Assad for what they said was his use of chemical weapons.

"I’m putting here the case that the Assad regime did this, and that the use of chemical weapons on a large scale like this cannot go unaddressed," U.K. Foreign Secretary William Hague told BBC Radio 4.

Hague said Britain is convinced Assad was behind the Aug. 21 attack in Ghouta, outside Damascus, and that there was agreement with the U.S. and France on the need to respond.

The U.K. government plans to decide tomorrow whether to recall Parliament and seek approval for taking action, according to a person familiar with discussions who asked not to be named.

U.S. Secretary of State John Kerry was scheduled to make a statement on Syria at 2 p.m. Washington time, the State Department said in an e-mailed statement.

Turkish Foreign Minister Ahmet Davutoglu said his country will join a “coalition” against Syria if the UN fails to act.

Syria’s government denies the accusations.

'Surgical' Strike

"I think a response is imminent," U.S. Senator Bob Corker of Tennessee, the ranking Republican on the Senate Foreign Relations Committee, said today on MSNBC. Corker said he expects "a surgical, proportional strike against the Assad regime for what they have done." Obama doesn’t need authorization from Congress to begin military action, he said.

Senator John McCain, an Arizona Republican, said the U.S. should use "standoff weaponry" to destroy Syrian airfields, fuel, and maintenance facilities.

"If the United States stands by and doesn’t take very serious action — not just launching some cruise missiles — then, again, our credibility in the world is diminished even more, if there’s any left," McCain told reporters today in Seoul.

Syrian authorities and opposition activists blamed each other for the gunfire aimed at the UN investigators. Ban said he told UN disarmament chief Angela Kane, who is in Damascus, to "register a strong complaint" with the Syrian government and opposition forces about the sniper attack "so that this will never happen" again.

'Massacre’s Origin'

The UN inspectors intend to continue their probe tomorrow, UN spokesman Farhan Haq told reporters in New York.

Israel’s Minister of Intelligence Yuval Steinitz said the use of chemicals was "clear." French Foreign Minister Laurent Fabius said it was "obvious" the weapons had been used and that the "massacre’s origin comes from the regime of Bashar al-Assad."

Russian Foreign Minister Sergei Lavrov accused the West of rushing to judgment before the UN inspectors complete their work. "Western leaders are making statements that indicate that they won’t wait for the results of this commission, they have already decided everything," he said.

Three hospitals in Syria’s Damascus governorate have reported seeing 3,600 patients displaying neurotoxic symptoms on the morning of Aug. 21, the Doctors Without Borders humanitarian group said. Of those patients, 355 reportedly died, the group said.

Constant Shelling

The integrity of the inspectors' findings may be compromised because constant shelling of the area in the five days since the purported attack could have corrupted or destroyed evidence, a U.S. administration official said in an e-mailed statement.

U.S. intelligence officials and international partners have concluded that chemicals were used, based on the reported number of victims, reported symptoms of those who were killed or injured in the Aug. 21 attacks, witness accounts and other facts gathered, according to the U.S. statement.

"There is very little doubt at this point that a chemical weapon was used by the Syrian regime against civilians in this incident," according to the official’s statement. The statement was released on condition of anonymity because the person wasn’t authorized to speak publicly.

'Drums of War'

West Texas Intermediate crude fell for the first time in three days as orders for U.S. durable goods dropped more than forecast in July and as Libya oil exports resumed from one of the closed ports. It gained earlier on speculation that tension in Syria would affect Middle East supplies. WTI for October delivery slid 53 cents, or 0.5 percent, to $105.89 a barrel at 12:17 p.m. on the New York Mercantile Exchange. Prices are up 15 percent in 2013.

Any military action against Syria may have “extremely dangerous” consequences for the region and recent U.S. statements have set off “deep alarm” in Russia, Lavrov told Kerry in a phone conversation yesterday, the Foreign Ministry in Moscow said on its website.

Hossein Sheikholeslam, the Iranian parliament’s director-general for international affairs, said nations are “beating the drums of war.” He told the state-run Fars news agency that Israel risks being the “victim” if any attempt is made to attack Syria.

Security Council

The U.K.’s Hague and Turkey’s Davutoglu signaled that action may be taken even without the backing of the UN Security Council, which has balked at strong action against the Assad government in the past.

"Is it possible to respond without complete agreement on the security council? I would argue yes it is," Hague said. "Other countries including France are very clear that we can’t allow the idea that chemical weapons in the 21st century can be used with impunity."

Assad has dismissed the accusations as "nonsense," telling the Russian newspaper Izvestia that allegations were "politicized." The U.S. will be faced with "failure" if it decides on the military option, Assad said. "America has waged many wars, but has never been able to achieve its political objectives from any of them," Assad said in the interview.

Obama said a year ago that the use of chemical weapons by the Assad regime would cross a U.S. “red line.” The U.S. now has four destroyers equipped with Tomahawk cruise missiles in the Mediterranean Sea, compared with three that have been there for months, according to a U.S. official familiar with the forces there. None of the ships — the USS Gravely, the USS Barry, the USS Mahan and the USS Ramage — has been assigned a mission, the official said.