BEIRUT - The United Nations stepped up demands on Syria for access to rebel-held Damascus suburbs hit by an apparent poison gas attack as activists sought to smuggle samples from victims to U.N. chemical weapons inspectors.
"I can think of no good reason why any party, either government or opposition forces - would decline this opportunity to get to the truth of the matter," U.N. Secretary General Ban Ki-moon told a diplomatic forum in Seoul on Friday.
Opponents of President Bashar al-Assad said they had been in contact with the specialist U.N. team in Damascus and had sent tissue samples with couriers seeking to slip across into the government-held city center to deliver them to the inspectors.
Adding to pressure on Assad, whose government denies responsibility for fumes that rebels say killed hundreds early on Wednesday, key ally Russia said it had urged Syria to cooperate with the U.N. mission.
China, however, called on all parties not to prejudge the outcome of the investigation. U.S. officials have suggested that evidence so far tends to point to an attack by Assad's forces.
The government has made no public comment on its willingness to let the inspectors cross the frontline from their hotel to the affected areas, some just a few minutes drive away. Its troops have been bombarding the suburbs, making it risky for any mission to reach the hospitals and morgues.
The longer the team waits for permission to investigate, the less likely they are to get to the bottom of an incident in which opponents say Syrian government forces fired rockets laden with poison gas canisters into rebel-held neighborhoods.
The group of experts finally arrived in Syria five days ago, after months of wrangling with Damascus over a mandate to examine sites of previous, smaller alleged chemical attacks. Ban is dispatching a top official to lobby the Damascus authorities to allow them to expand their inquiries to the latest incident.
The U.N. special envoy on Syria, Lakhdar Brahimi, said he believed the poisoning should accelerate efforts by divided world powers to mount a new coordinated push for peace talks.
Speaking from the town of Arbin, one of those affected by mysterious deaths from poisoning, opposition activist Abu Nidal told Reuters: "The U.N. team spoke with us and since then we prepared for them samples of hair, skin and blood and smuggled them back into Damascus with trusted couriers."
Several others in neighboring districts said they, too, had prepared samples to smuggle into the capital but had been unable to find a way to access the U.N. monitors inside their hotel.
The administration of U.S. President Barack Obama said it was "appalled" by the deaths but has made clear any response would await confirmation of a chemical attack and its origin.
Last year, Obama said the use of chemical weapons by Assad's forces would be a "red line" triggering unspecified U.S. action. But Washington's response to evidence of poison gas being deployed has been muted. In June, it said it would help arm the rebels, but not taking military action itself against Assad.
A U.S. official familiar with initial intelligence assessments said Wednesday's gassing appeared to be the work of the Assad government.
Images, including some by freelance photographers supplied to Reuters, showed scores of bodies laid out on floors with no visible signs of injury. Some had foam at the nose and mouth.
French Foreign Minister Laurent Fabius said on Thursday that world powers must respond with force if allegations that Syria's government was responsible for the deadliest chemical attack on civilians in a quarter-century prove true. But Fabius stressed there was no question of sending in troops on the ground.
A forceful foreign response is unlikely to be translated into rapid, concerted action given Washington's cautious tone and divisions between Western powers and Russia and China.
Moscow, however, is also urging Assad to accept the investigation, arguing that rebels may have released gas to discredit the president. On Wednesday, Russian and Chinese objections to Western pressure on Syria saw the Security Council merely call in vague terms for "clarity" - a position increasingly frustrated Syrian rebels described as "shameful".
Syrian officials say allegations against their forces are "illogical and fabricated". They point to the timing of the attack, just days after U.N. inspectors arrived, and say it conflicts with previous assurances that, if they possessed chemical weapons, they would never use them against Syrians.
Former weapons investigators say every hour matters in determining if chemicals were used and who was behind them.
"The longer it takes, the easier it is for anybody who has used it to try to cover up," said Demetrius Perricos, who headed the U.N. team of weapons inspectors in Iraq in the 2000s.
European officials speaking on condition of anonymity said that hypothetically, options for response range from air strikes, creating a no-fly zone, or providing heavy weapons to some rebels were all still on the table. But there was little prospect of concrete measures without U.S. backing.
"The American reaction ... was cautious," said one official. "And without U.S. firepower, there's little we can do."
Obama has directed U.S. intelligence agencies to urgently help establish what caused the deaths, a State Department spokeswoman said, but she said it may be difficult given that the United States does not have diplomatic relations with Syria.
No deadline was given to agencies investigating the attack, she said.
"At this time, right now, we are unable to conclusively determine CW (chemical weapons) use," the State Department's Jen Psaki told reporters. "We are doing everything possible in our power to nail down the facts," she added.
The State Department also said senior U.S. and Russian diplomats would meet in The Hague next Wednesday to discuss ending Syria's two-year civil war, which has already killed more than 100,0000 people. It would be the first such meeting since allegations of the chemical attack.
A senior State Department official said chemical weapons would also be discussed at the meeting.
Syria's revolt against four decades of Assad family rule has turned into a brutal civil war that has killed more than 100,000 people in two and a half years and divided the Middle East along largely sectarian lines.
Assad's Alawite sect is an offshoot of Shi'ite Islam and has the backing of Shi'ite powers Iran and Lebanese Shi'ite militant group Hezbollah. Western powers back the opposition but have been reluctant to fully commit to an Arab Sunni-backed revolt increasingly overtaken by Islamists linked to al Qaeda.
Millions have been forced from their homes. On Friday, the United Nations said one million children alone have fled the country and two million have been displaced inside Syria.