U.S. President Barack Obama says this week's alleged chemical attack in Syria was a "big event of grave concern."
"And we are already in communications with the entire international community," Obama added. "We're moving through the UN to try to prompt better action from them, and we've called on the Syrian government to allow an investigation of the site, because the UN inspectors are on the ground right now."
In a CNN interview broadcast on August 23, Obama said if the allegations proved true, the situation would "require America's attention."
But Obama added that "the notion that the [United States] can somehow solve what is a sectarian complex problem inside of Syria sometimes is overstated."
Britain said it believed forces loyal to Syrian President Bashar al-Assad were responsible for the reported chemical weapons attack on August 21 near Damascus.
Syrian opposition sources have estimated that between 500 and 1,300 people died in the alleged gas attack. The government denies using chemical weapons.
British Foreign Secretary William Hague said at a news briefing on August 23 that "it seems Assad's regime has something to hide."
"This is our priority at the moment -- to make sure that the UN team can investigate on the ground and establish the facts," Hague added.
"If that doesn't happen though within some days -- since time is of the essence in these things, the evidence will deteriorate over a matter of days -- then we will need to be ready to go back to the [UN] Security Council to get a stronger mandate and for the world to speak together more forcefully about this so that there can be access."
In South Korea, UN Secretary-General Ban Ki-moon called for the Syrian government's cooperation with visiting UN chemical weapons investigators regarding the alleged attack near Damascus on August 21.
"Any use of chemical weapons -- anywhere, by anybody, under any circumstances - would violate international law," Ban said on August 23. "Such a crime against humanity should result in serious consequences for the perpetrator."
Russia has accused the opposition of preventing an objective investigation into the alleged attack.
The Russian Foreign Ministry also criticized as "unacceptable" calls for the use of force against the Syrian regime.
Moscow said on August 23 it had "called on the Syrian government to cooperate with the UN chemical experts."
But the Russian Foreign Ministry, in a statement, also said evidence was mounting that the attack was "clearly provocative in nature."
The main Syrian opposition group said on August 23 it would ensure the safety of UN chemical weapons inspectors in areas it controls.
The Syrian National Coalition said it was "critical" that the UN inspectors reach the site of the alleged gas attack within 48 hours.
The UN inspectors arrived in Damascus on August 18 to investigate previous allegations of chemical-weapons attacks made against both sides.
The United States says it has so far been unable to conclusively say whether chemical weapons were used in the attack.
State Department spokeswoman Jen Psaki said U.S. officials were doing everything possible to learn the facts about the alleged attack.
She said Obama has directed U.S. intelligence agencies to work to help verify allegations made by opposition forces that Syrian government forces supporting Assad carried out the reported attack.
Charles Duelfer, the former chief of the Iraq Survey Group, which searched for weapons of mass destruction in Iraq after the U.S. invasion in 2003, gave his assessment of video images purportedly from the attack.
"This is quite powerful and it's clearly something that hasn't been faked," he said. "I mean, these are real people. You couldn't create this, much to the -- I know there are some international parties that say, well, this could be something created, a 'provocation,' in the words of the Russian foreign minister. That's not a convincing position."
Meanwhile, the United Nations says the number of children who have been forced to flee Syria because of the civil war has reached 1 million.
The UN Children’s Fund, UNICEF, and the UN refugee agency, UNHCR, said that another 2 million Syrian youths have been displaced from their homes inside Syria.
Ahmed, a 14-year-old boy from southwestern city of Daraa, told the UNHCR about his family's suffering.
"My brother was killed and my sister experienced a brain injury," he said. "We thought we could not bring her here at first. But in the end we brought her and my brother's body in an ambulance. We ended up burying him here. My sister has been receiving treatment to learn how to walk again after the accident because she lost usage of her left leg. I wish we could go back home one day."
A total of 2 million people are estimated to have fled Syria since the war began 2 1/2 years ago.
UN agencies say children often come under attack or are recruited as fighters in violation of humanitarian law.
UN figures show that some 740,000 Syrian refugees are under the age of 11.
Most refugees from the Syrian conflict have wound up in Turkey, Lebanon, Iraq, Jordan, and North Africa.
With reporting by Reuters, AFP, and dpa