US President Barack Obama said on Saturday there should be a military strike on Syria in response to an August 21 poison gas attack which US intelligence officials said killed more than 1,400 people.
However Obama signalled a delay in what had appeared to be an imminent strike on Syria, by saying he would seek approval from Congress for a strike, a move a Syrian state newspaper described as a the start of a "historic American retreat".
In his first comments since Obama's speech, Assad said: "Syria ... is capable of confronting any external aggression," state television quoted him as saying during a meeting with Iranian officials.
"The American threats of launching an attack against Syria will not discourage Syria away from its principles ... or its fight against terrorism supported by some regional and Western countries, first and foremost the United States of America."
Syria generally refers to rebels fighting to topple Assad as "terrorists".
Syrian Deputy Foreign Minister Faisal Mekdad said on Sunday Obama's speech showed hesitation and confusion.
"It is clear there was a sense of hesitation and disappointment in what was said by President Barack Obama yesterday. And it is also clear there was a sense of confusion as well," he told reporters in Damascus.
An editorial in al-Thawra newspaper, Syria's official daily also criticised Obama's move to go to Congress.
"Obama announced yesterday, directly or through implication, the beginning of the historic American retreat," said the comments, which were carried in a front-page editorial in Syria's official al-Thawra newspaper.