UN-Arab League envoy Lakhdar Brahimi is pushing "extremely hard" for a ceasefire in Syria and will brief the UN Security Council on Wednesday on his efforts, the UN spokesman said.
Brahimi is now back in Cairo following talks with Syrian President Bashar al-Assad in Damascus, UN spokesman Martin Nesirky told reporters.
Nesirky had previously said that Brahimi and Assad held "frank and substantive" talks and that the Syrian leader had given a "positive reaction" to UN calls for a ceasefire during a Muslim holiday this week.
Brahimi has also appealed to the Syrian opposition to halt the 19-month-old conflict but fighting has raged all week across the country despite the calls.
"It remains to be seen what will happen" about the ceasefire, Nesirky said Tuesday. "Mr Brahimi is pushing extremely hard as is the secretary general because this is an extremely important moment."
Nesirky said the international mediator wanted "a long-lasting ceasefire that will enable a political process to unfold."
Brahimi will address the 15-member Security Council by video on Wednesday.
The council remains bitterly divided over the Syria conflict.
Western nations have pressed for international action on the conflict, but Russia and China have vetoed three council resolutions that could have led to sanctions against the Assad government.
Russia has proposed a council statement backing Brahimi's calls for a ceasefire. Russia's UN ambassador Vitaly Churkin said he was "disappointed" that it has not yet been agreed.