WASHINGTON: U.S. Secretary of State John Kerry said Monday that the evidence of a massive deadly chemical attack last week was “undeniable” and accused the Syrian government of trying to cover it up, signaling the United States was possibly edging closer to a military response.

 

Kerry spoke several hours after U.N. chemical weapons experts interviewed and took blood samples from victims of last week’s apparent chemical attack in a rebel-held suburb of Syria’s capital, after the inspectors themselves survived sniper fire that hit their convoy.

 

In the most forceful U.S. reaction yet after Wednesday’s suspected gas attack outside Damascus, Kerry said President Barack Obama “believes there must be accountability for those who would use the world’s most heinous weapons against the world’s most vulnerable people.”

 

“What we saw in Syria last week should shock the conscience of the world,” Kerry told reporters. “Let me be clear: The indiscriminate slaughter of civilians, the killing of women and children and innocent bystanders by chemical weapons is a moral obscenity.”Kerry accused the government of President Bashar Assad of acting like it had something to hide by blocking the U.N. inspectors’ visit to the scene for days and shelling the area.

 

“Our sense of basic humanity is offended not only by this cowardly crime, but also by the cynical attempt to cover it up,” Kerry said.

 

The information so far, including videos and accounts from the ground, indicate that chemical weapons were used in Syria, he said.

 

“It is undeniable,” he said, adding that it was the Syrian government that maintained custody of chemical weapons and had the rockets capable of delivering them.

 

Kerry stopped short of explicitly blaming the Syrian government for the gas attack but strongly implied that no one else could have been behind it and said the United States had additional information it would provide in the days ahead.

 

There were mounting signs that the United States and Western allies were laying the groundwork for some kind of military response to the incident, which took place a year after Obama declared the use of chemical weapons a “red line” that would require strong action.

 

Military chiefs from the United States, Britain, France, other NATO allies and the main anti-Assad countries in the region, including Saudi Arabia and Turkey, met in Jordan Monday for what could be a council of war, should they decide to punish Syria.

 

However, the administration has not set a timeline for responding to the alleged chemical attacks, State Department Marie Harf said shortly after Kerry’s speech.

 

The chairman of the U.S. Joint Chiefs of Staff, Martin Dempsey, co-hosted the Amman meeting with his Jordanian counterpart. He has been one of the voices in Washington urging caution and emphasizing the costs of a full-scale military intervention in a war in the heart of the Middle East.

 

In Damascus, U.N. investigators crossed the front line from the center of the city, which remains under Assad’s control, to inspect the Moadamieh suburb, one of at least four neighborhoods hit by the poison gas last Wednesday before dawn.

 

The United Nations said one vehicle in its convoy was crippled by gunshots fired by “unidentified snipers.” The team continued on after turning back for a replacement car.

 

Wassim al-Ahmad, an opposition activist, said members of the Free Syrian Army umbrella rebel organization and the opposition’s Moadamieh Local Council were accompanying the inspectors on their tour of the suburb.

 

Video filmed at the site showed inspectors in black and blue body armor and blue U.N. helmets walking through a street as curious onlookers came up to watch.

 

They shook hands with men who appeared to be rebels wearing camouflage vests. The group descended into the basement of a building where they were told injured survivors were being treated to protect them from more shelling. Another video showed an inspector interviewing a patient and taking notes.

 

Activists say at least 80 people were killed in Moadamieh when the district was hit with poison gas. Hundreds of people also were killed in three other rebel-held districts – Arbin, Ain Tarma and Jobar.

 

An opposition activist said a large crowd of people gathered to air their grievances to the U.N. inspectors, who planned to take samples from corpses.

 

The inspectors later returned to their hotel, and within an hour residents reported that the shelling of Moadamieh resumed.

 

The decision to proceed with the mission despite coming under attack thwarted an apparent attempt to halt their work before it began.

 

“The first vehicle of the Chemical Weapons Investigation Team was deliberately shot at multiple times by unidentified snipers in the buffer zone area,” the United Nations said in a statement.

 

“It has to be stressed again that all sides need to extend their cooperation so that the team can safely carry out their important work.”

 

Syrian state television blamed rebel “terrorists” for the shooting. The opposition blamed it on pro-Assad militiamen.

 

U.S. Defense Secretary Chuck Hagel said any military response to the apparent use of chemical weapons would be coordinated with allies.

 

“The United States is looking at all options regarding the situation in Syria,” he said. “We’re working with our allies and the international community.”

 

British Prime Minister David Cameron cut short a holiday to lead a top-level security meeting.

 

Russian President Vladimir Putin spoke to Cameron Monday, saying there was no evidence yet the regime had used chemical weapons.

 

Iranian Foreign Minister Mohammad Javad Zarif reiterated to U.N. Undersecretary-General Jeffrey D. Feltman Tehran’s support for a political, rather than military solution, to the crisis.