A child stands on the remnants of a destroyed military vehicle in front of a damaged building in Al Inzarat district in Aleppo on Feb. 17, 2013. (STRINGER/REUTERS)

A U.N. envoy on Sunday intensified pressure on the Syrian government to accept an opposition offer to negotiate an end to the country’s 23-month old conflict, amid continued violence that underscored the difficulty of bringing about any form of political settlement.

Lakhdar Brahimi, the joint U.N.-Arab League envoy to Syria, told reporters in Cairo that opposition leader Moaz al-Khatib’s initiative aimed at opening negotiations with representatives of Syrian President Bashar al-Assad’s government remains very much “on the table” after it received an endorsement from the wider opposition on Friday.

The offer was initially announced on Facebook by Khatib, the president of the umbrella National Coalition for Syrian Revolutionary and Opposition Forces, stirring outrage from other members of the coalition, who claimed they had not been consulted. The opposition has long rejected talks with any representatives of Assad’s regime, holding it responsible for the more than 60,000 deaths reported by the U.N. since the revolt erupted in March 2011.

But in a statement Friday, the coalition said that while it continues to reject a role for Assad and the leadership of his security apparatus, it would accept talks with any other Syrians, including those serving with the government, “as long as they did not participate in any crimes.”

The United Nations is willing to host the discussions and it is now up to the Syrian government to identify an “acceptable delegation,” Brahimi said.

The offer “challenges the Syrian government to fulfill its often-repeated assertion that it is ready for dialogue and a peaceful settlement,” he added.

But comments by the speaker of Syria’s People’s Assembly in Damascus highlighted how far apart the two sides to the conflict remain. According to the official Syrian Arab News Agency, Mohammed Jihad al-Laham told a session of the parliament, dominated by members of Assad’s Baath Party, that dialogue should be based on Assad’s political reform program, which envisions a continued role for Assad and limited talks with handpicked members of the opposition.

“That is a million miles away from what the national coalition has put forward,” said Salman Shaikh, director of the Brookings Doha Center in Qatar. “This effort is not going to gain any traction any time soon.”

Brahimi’s efforts to promote a political solution come against a backdrop of intensified rebel offensives in the north, east and center of the country that have seen the rebels make significant gains in recent days.

On Sunday, rebel fighters in the strategic northern city of Aleppo upheld their attacks against the international airport, and two military airports in the province, building on a string of successes against government air bases and other military facilities in recent months.

Overnight Saturday, activists reported that government forces had fired a number of Scud-like ballistic missiles toward the northern provinces where the rebels are advancing.

Rebel forces also have been making gains in the eastern province of Hasaka, and the extremist al-Nusra Front, suspected of links to the wider al-Qaeda franchise, appears to be playing a leading role. The Britain-based Syrian Observatory for Human Rights posted a video it said it received Sunday showing the execution by al-Nusra fighters of five men identified as Shiite Alawites last Tuesday at an oil facility in the eastern town of Shaddadi, after government forces were driven out.

In Damascus, electricity returned after an overnight blackout that also affected several other parts of the country. Syria’s Prime Minister Wael al-Halqi told the parliamentary session that the government is now able to meet only 50 percent to 60 percent of the country’s electricity needs because rebel attacks on the country’s infrastructure are “growing increasingly frequent and more systematic.”

He also blamed economic sanctions imposed by the United States and Europe for widespread shortages of medical supplies and other goods, describing Syria’s challenges as “beyond the capacity and the ability of any country to bear.”

Iran has stepped in to resolve a nationwide shortage of flour, he said, and medicines have been procured from Iran, China, Pakistan and India.

Supplying Aleppo, where government forces are increasingly cut off from the rest of the country, has become problematic, however, because of “terrorist” attacks on convoys traveling along the roads, he said.

Syrians have “no need to fear” that their economy is in trouble, he insisted, but his comments nonetheless suggested the government is feeling the twin pressures of the rebel offensive and international sanctions.