The United Nations will publish a report Monday by a team of chemical inspectors on a deadly attack outside Damascus last month that killed hundreds and triggered a large international effort to rid the Syrian regime of its chemical arms.

The report, which was handed to Secretary General Ban Ki-moon on Sunday, is expected to confirm that there was a chemical attack, and may also finger the regime of Syrian President Bashar Assad for launching the attack.

Ban said Friday that he believes there will be “an overwhelming report” that chemical weapons were used in the attack.

UN spokesman Martin Nesirky said the secretary-general will brief a closed session of the UN Security Council on its contents Monday morning. He will also brief the 193-member General Assembly later in the day.

UN associate spokesman Farhan Haq said the media should receive it shortly afterward.

The inspection team, led by Swedish expert Ake Sellstrom, was mandated to report on whether chemical weapons were used in the August 21 attack in the Damascus suburb of Ghouta and, if so, which chemical agents were used — not on who was responsible.

However, two UN diplomats said the report could point to the perpetrators, saying that the inspectors collected many samples from the attack and also interviewed doctors and witnesses.

The two diplomats said the inspectors had soil, blood and urine samples and may also have collected remnants of the rockets or other weapons used in the attack, which could point to those responsible. The diplomats spoke on condition of anonymity because discussions on the issue have been confidential.

There is near certain belief in UN diplomatic circles that the deaths were caused by a chemical weapon, and the nerve agent sarin is the main suspect.

The diplomats believe Sellstrom’s team can figure out what happened from what one called “the wealth of evidence” they collected.

A determination of the delivery system used in the attack, and the composition of the chemical agent, could point to the perpetrator, they said.

Haq said the UN has made some efforts to speed up the analysis, noting that instead of two laboratories, the samples are being tested at four laboratories in Europe. The testing could have taken three to four weeks, but the secretary-general has been pressing for a speedier report.

One diplomat said Russia, a strong ally of Syria, was putting heavy pressure on Sellstrom to restrict his findings, but whether he does so remains to be seen. Ban could possibly go beyond the inspectors’ findings and characterize who did it, the diplomat said.

If Sellstrom’s report points to a perpetrator, there is certain to be demands for proof from the other side.

The report will come two days after the US and Russia signed an agreement that will Syria stripped of its chemical weapons that will then be destroyed. The US came to the deal after a flurry of diplomatic activity between Damascus, Washington and Moscow aimed at averted a punitive US strike on the Syrian regime in response to the chemical attack.

Russia still maintains that the attack was carried out by rebels to frame the Assad regime.

Damascus, considered to have one of the world’s largest stockpiles of chemical arms, is expected to report on all of its chemical arms by the end of the week and hand them over for destruction by mid-2014, as part of joining an international chemical weapons ban treaty. Syria touted the deal as a “victory.”

Israeli and American officials have expressed cautious optimism over the deal, though on Saturday US President Barack Obama warned that military action was still on the table should diplomacy fail.

The US, Britain, France and a number of NGOs have already said they believe sarin gas or another chemical was used in the attack, which was carried out by regime soldiers. The US says over 1,400 people were killed, while others cite lower death tolls.