Exclusive: Deputy PM says neither side is strong enough to win and government may call for ceasefire at Geneva talks

The Syrian conflict has reached a stalemate and President Bashar al-Assad's government will call for a ceasefire at a long-delayed conference in Geneva on the state's future, the country's deputy prime minister has said in an interview with the Guardian.

Qadri Jamil said that neither side was strong enough to win the conflict, which has lasted two years and caused the death of more than 100,000 people. Jamil, who is in charge of country's finances, also said that the Syrian economy had suffered catastrophic losses.

"Neither the armed opposition nor the regime is capable of defeating the other side," he said. "This zero balance of forces will not change for a while."

Meanwhile, he said, the Syrian economy had lost about $100bn (£62bn), equivalent to two years of normal production, during the war.

If accepted by the armed opposition, a ceasefire would have to be kept "under international observation", which could be provided by monitors or UN peace-keepers – as long as they came from neutral or friendly countries, he said.

Leaders of Syria's armed opposition have repeatedly refused to go to what is called Geneva Two unless Assad first resigns. An earlier conference on Syria at Geneva lasted for just one day in June last year and no Syrians attended.

Jamil's comments are the first indication of the proposals that Syria will bring to the table at the summit, which Russia and the US have been trying to convene for months.

Asked what proposals his government would make at Geneva, he said: "An end to external intervention, a ceasefire and the launching of a peaceful political process in a way that the Syrian people can enjoy self-determination without outside intervention and in a democratic way."

Although both Moscow and the Obama administration seem committed to convening Geneva Two, a major split has emerged between Russia and the US over who should take part. The US has been urging the Syrian National Coalition, the western-backed rebel group, to drop its boycott but wants the SNC to be the only opposition delegation.

"The paradox now is that the US is trying to give the SNC the leading role. We're fed up with this monopolistic view," Jamil said.

Jamil is one of two cabinet ministers from small secular parties who were appointed last year to end the monopoly of the Ba'ath party.

By joining the government, he said, "we wanted to give a lesson to both sides to prepare for a government of national unity and break the unilateral aspect of the regime – and break the fear in opposition circles about sitting in front of the regime".

Jamil's comments on why he joined the cabinet were those of his party, but his other comments in the hour-long interview represented the government's position, he said.

He repeatedly stressed Syria was changing but it needed support rather than pressure. "Let nobody have any fear that the regime in its present form will continue. For all practical purposes the regime in its previous form has ended. In order to realise our progressive reforms we need the west and all those who are involved in Syria to get off our shoulders," he said.

Jamil said that last week's UN report on the 21 August chemical weapons attack which killed more than 1,000 people was "not thoroughly objective".

He said Russia had produced evidence showing the rockets that were identified by the UN inspectors as carrying sarin were indeed Soviet-made. But he said they had been exported from Russia to Libya in the 1970s.

"They were loaded with chemicals by Gaddafi and exported to fundamentalists in Syria after Gaddafi fell," he said.

On Friday Vladimir Putin said he could not be sure that Assad would fulfil the US-Russian plan to identify and destroy his chemical weapons stocks, but "all the signs" suggested the Syrian regime was serious.

"Will we be able to accomplish it all? I cannot be 100% sure about it," said Putin, speaking at a discussion forum with western politicians and Russia experts in the north-west of the country. "But everything we have seen so far in recent days gives us confidence that this will happen … I hope so."

Details of Russia's position on who should represent the opposition at Geneva Two have also emerged. Members of the National Co-ordination Body for Democratic Change in Syria, an umbrella group for several internal parties, met Sergei Ryabkov, a Russian deputy foreign minister, in Damascus on Thursday evening.

Safwan Akkash, an NCB leader, told the Guardian afterwards that Ryabkov told them Russia was proposing there should be three opposition teams at Geneva. These should be the NCB, the Syrian National Coalition, and a combined delegation of Kurds.

The SNC, while cautiously accepting Geneva Two as a means of breaking an entrenched stalemate, insists that Assad's resignation remains non-negotiable.

It is also sticking to a position that a transitional government must follow the ousting of Assad.

It has remained insistent that those who carried out the chemical attack must be held to account – a point it has hammered home ever since the Russian-US deal to force Syria to hand over its chemical weapons stockpiles.

• This article was amended overnight on 19-20 September 2013. It originally attributed the use of the term 'civil war' to Qadri Jamil. He did not use this term during the interview. This has been corrected.