He spoke as UN Security Council members negotiate a resolution on how to respond if Syria fails to fulfil an international deal to eliminate its chemical weapons arsenal.
The United States, Britain and France want a tough resolution that could include sanctions or the use of force if Syria fails to follow through, but Russia opposes such language.
Assad told CCTV Damascus would carry out its commitments, but warned that militants obeying outside powers might try to make it seem otherwise.
"We know that those terrorists follow the orders of other countries," he said, in an online video of the interview.
"And these countries might incite the terrorists to block the inspectors from arriving, in order to blame the Syrian government for obstructing the implementation of the agreement."
Under the plan, a tentative deadline of last Saturday was set for a full accounting of Syria's chemical arsenal, which is to be destroyed by mid-2014.
The Hague-based Organisation for Prohibition of Chemical Weapons, which is overseeing the process, said Saturday it had received a complete inventory from Syria and was scrutinising the data.
Assad acknowledged the arsenal was big, and said it was manufactured in the 1980s and 1990s to counter neighbour and rival Israel.
"Syria has manufactured these chemical weapons for decades so naturally the quantities will be large," he said. "We're a country at war and we have territory that has been occupied for over 40 years."
Nonetheless "we will honour everything that we have agreed to do", he was quoted on CCTV's website as saying.
Assad was further quoted as accusing the US, Britain and France of "trying to make themselves winners in a war against a Syria which is their imaginary enemy".
But he expressed confidence that fellow veto-holding Security Council members China and Russia would block Western efforts to authorise the use of force against his country.
"China and Russia are playing a positive role in the UN Security Council to ensure any excuse for military action against Syria will not stand," he was quoted as saying.
"Thus Syria should not be concerned by any such draft or deal."
There are hopes the deal could pave the way for talks to end the 30-month conflict, which has killed more than 110,000 people and forced two million to flee abroad.
The agreement headed off US military action against Damascus and is now to be enshrined in a UN resolution.
Most Western governments and the Syrian opposition accuse forces loyal to Assad of unleashing chemical weapons that killed hundreds last month.
He denies mounting the attack.