The United Nations formally accepted Syria's application to join the chemical weapons convention, a spokeswoman said.
The move adds another piece to the diplomatic plan to end the threat of a US military strike on President Bashar al-Assad over the suspected use of chemical arms in the 30-month-old Syria conflict.
Syria applied Thursday to join the convention, which bans the production and stockpiling of chemical weapons and orders the destruction of existing stocks. But UN lawyers asked the government for information before it could be accepted.
UN leader Ban Ki-moon "has today received the formal instrument of accession to the convention by the Syrian Arab Republic," said a UN spokeswoman Vannina Maestracci, signaling the end of any doubts.
She added that the convention will enter into force for Syria on October 14 - 30 days after the date of the formal acceptance.
Ban "welcomes" Syria's accession, Maestracci added.
Assad's joining the convention and the related Organisation for the Prohibition of Chemical Weapons is part of a plan drawn up by Russia and the United States to head off a western military strike.
The United States and other western nations accuse Assad's forces of launching a sarin gas attack on August 21 near Damascus in which hundreds died. The government blames opposition rebels for the attack.