The Syrian government has been urged to present its plan for political change in the country next week at the Geneva peace talks, UN Syria envoy Staffan de Mistura said Friday.
After a five-year civil war, a ceasefire has allowed negotiations to take place but the future of President Bashar al-Assad is a major sticking point, with the government yet to put forward proposals.
"I'm not disappointed, I'm just pushing," de Mistura said after five days of shuttling between the government delegation and opposition representatives.
The opposition already handed in their plan for a political transition process on Thursday.
"We are in a hurry," de Mistura said, expressing hope that the next round of talks in April would be much more in-depth than the current negotiations, which are scheduled to end next Thursday.
According to de Mistura, the government and opposition do not yet share any common ground on a political transition process.
While al-Assad has given no indication that he is willing to relinquish power, the opposition says he cannot rule any longer.
Delegates of the exiled opposition said the Syrian government lacks the will to conduct negotiations on political change.
"At the moment there is no partner on the other side who is willing to engage," leading opposition negotiator Bassma Kodmani told dpa.
"We're waiting for a change of attitude as a result of Russian pressure. This has not come yet," she said, referring to the military and political alliance between the governments in Moscow and Damascus.
Al-Assad's chief negotiator Bashar al-Jaafari said Friday that his side was still focussed on getting the opposition to agree on a set of basic principles for the talks.
"We believe that the adoption of these principles, that we have called fundamental elements, will lead to a serious intra-Syrian dialogue to help build the future of our country," al-Jaafari said.
Kodmani said al-Assad should leave before planned elections, which the UN Security Council has said should take place within 18 months.
"There will be no free elections as long as he is in charge of everything," she said.
De Mistura has also consulted with opposition figures this week who have remained in Syria and are seen as closer to the government.
Ahmad Alkoussa, a delegate of the so-called internal opposition, rejected the idea that the president would have to step down before a national vote.
"Syrian President Bashar al-Assad is an elected president from the people, and only the people can decide on it," he said in Geneva.
The current round of Geneva talks was made possible by a fragile ceasefire that was brokered by the United States and Russia.
However, the truce agreement does not include the extremist militia Islamic State.
At least 16 people including eight children were killed Friday when planes raided Islamic State's de-facto capital al-Raqqa in northern Syria, a monitoring group said.
The Britain-based Syrian Observatory for Human Rights did not say if the air raids in several areas of al-Raqqa were carried out by Russian, government or US-led coalition planes.
Meanwhile Amaaq news agency, which has links to Islamic State, reported that the extremist group killed five Russian soldiers in fighting near the ancient city of Palmyra.
Syrian regime forces backed by Russian planes launched an attack last week on Islamic State positions in the UNESCO World Heritage city.
Russian President Vladimir Putin on Monday ordered a withdrawal of the majority of Russian forces in Syria.
But Moscow asserted Friday that it will continue bombing Islamic State as well as al-Nusra Front, an affiliate of al-Qaeda.