- NEW: Syria sends British lawmakers a letter asking them to not take military action
- U.N. weapons inspectors are set to leave Syria by Saturday
- Obama: Evidence suggests the Syrian regime used chemical weapons on civilians
- Death toll estimates from an alleged chemical attack last week top 1,000
(CNN) -- The British government will publish Thursday some of its intelligence related to the alleged chemical weapons attack in Syria, British Prime Minister David Cameron's office said Thursday.
The announcement comes a day after U.S. President Barack Obama said there's no doubt that Syria launched chemical weapons attacks against its own people.
Chemical weapons in Syria: How did we get here?
Western countries are mulling possible military action against Syrian forces after the alleged chemical assault near Damascus on August 21. Death toll estimates range from several hundred to 1,300.
Syria crisis prompts Israeli preparations Syrian President Bashar al-Assad's regime has blamed rebels for the attack, a claim that Obama said was impossible.
Amanpour on chemical attacks 
What a U.S. strike on Syria might entail "We have looked at all the evidence, and we do not believe the opposition possessed ... chemical weapons of that sort," he told "PBS NewsHour" Wednesday.
"We do not believe that, given the delivery systems, using rockets, that the opposition could have carried out these attacks. We have concluded that the Syrian government in fact carried these out. And if that's so, then there need to be international consequences."
Ghitis: 5 reasons U.S. must intervene in Syria
A team of U.N. weapons inspectors is in Syria trying to determine whether chemical weapons were used. The inspectors are expected to leave Syria by Saturday morning, U.N. Secretary General Ban Ki-moon said Thursday, according to Ban's spokesman.
Opinion: Why western intervention in Syria will leave chaos
Britain's Parliament will vote on a motion Thursday that would rule out any possible military action until the U.N. inspectors reveal their findings to the U.N. Security Council. Afterward, the British Parliament will take another vote.
But Syria tried to proactively thwart any British military action by writing a letter to U.K. lawmakers.
Syria: Who wants what after chemical weapons horror
On Thursday, British members of parliament received an open letter from the Syrian government urging them not to take any military action against Syria, the press office for House of Commons Speaker John Bercow said.
Those who claimed to have survived the alleged chemical weapons attack described a horrific scene in the town of Zamalka.
"After the chemicals, they woke us up and told us to put masks on," a 6-year-old boy said, describing the alleged attack.
"I told my dad I can't breathe. My father then fainted and I fainted right after that, but we were found and taken to the emergency room."
CNN obtained video of the boy and others who made the claims to a journalist in the area.
CNN's Bharati Naik contributed to this report.
