BEIRUT (Reuters) - Syrian President Bashar al-Assad said on Monday any ceasefire did not mean each side had to stop using weapons, and nobody was capable of securing the conditions for one within a week.

"Regarding a ceasefire, a halt to operations, if it happened, it doesn't mean that each party will stop using weapons," Assad said in Damascus in televised comments.

"A ceasefire means in the first place halting the terrorists from strengthening their positions. Movement of weapons, equipment or terrorists, or fortification of positions, will not be allowed," he said.

World powers agreed in Munich on Friday to a "cessation of hostilities", scheduled to start a week later, but Syrian army offensives across the country, backed by Russian air strikes, continue unabated.

He said that there were many questions before a ceasefire could happen, including defining who is a terrorist, adding that as far as the state is concerned, anyone who carried a weapon against it was a terrorist.

"There can't be a ceasefire without a goal or a time. So far they say they want a ceasefire within a week. Who is capable of gathering all these conditions and requirements within a week? Nobody," Assad said.

"Who will talk to the terrorists? If a terrorist group rejects the ceasefire, who will hold it to account?"

If the terms of ceasefire are agreed, operations must be stopped with the aim of improving the security situation in order to reach local reconciliation agreements with rebels, he said.

Local reconciliation agreements are widely seen as a way for the state to pacify areas on its terms.

Assad also said that any political transition in the country must be subject to the existing Syrian constitution.

"Any transitional process, regardless of what it is, must be subject to the current constitution," he said, adding the suggestion of having "a transitional governing body" was a departure from the constitution.

"We can only stop working with the current constitution if we agree, in dialogue, to a new one that the Syrians vote on," he said.

(Reporting by Lisa Barrington and Tom Perry; Editing by Alison Williams)