Walid Muallem accused Western states of supplying chemical weapons to the Syrian opposition in a speech in which he called for an end to sanctions not only against his own country but also Iran, North Korea, Belarus and Venezuela.
"There is no civil war in Syria, but it is a war against terror," Muallem told the annual summit at United Nations headquarters in New York.
"Terrorists who used poisonous gases in my country have received chemical agents from regional and Western countries that are well known to all of us," the minister added.
The United States has accused President Bashar al-Assad's forces of staging an August 21 chemical weapons attack in which 1,400 people died. The threat of a US military strike with French backing was only called off with a Russia-US plan to destroy Syria's chemical weapons.
"Well-known states revealed their true face, and threatened with blatant military aggression outside the mandate (of the) Security Council (an) immoral, illegal and unilateral coercive measure," Muallem said.
The minister said there had to be a halt to foreign financing and arms supplies to the "terrorists" -- the government's habitual name for the opposition groups Assad has been battling for 30 months.
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Muallem said the government supported a negotiated settlement but the country's future could only be settled in "free and fair elections." Assad has announced he will stand in a new election in 2014.
"It is now for those who claim to support a political solution in Syria to stop all hostile practices and policies against Syria, and to head to Geneva without preconditions."
UN leader Ban Ki-moon has said he wants to organize a peace conference in the Swiss city in mid-November, but significant obstacles remain.
The conference would be to decide how to implement a Geneva declaration agreed by the major powers in June 2012 that there has to be a transitional government in Syria.
Opposition groups insist that Assad must stand down.
Ban held his first meeting with Syrian National Coalition chief Ahmad Jarba on Saturday to press the case for the opposition to overcome its divisions.
Muallem was adamant at the weekend that Assad's future is not up for discussion.
"Ballot boxes for free and fair elections remain the only solution to decide the options of the Syrian people in determining their own future away from the pressures of terrorism and foreign dictations," Muallem told the UN assembly.