KABUL, Afghanistan — Western leaders are banking on a national peace council set to begin here on Wednesday to start a new chapter in Afghanistan’s political life, bringing the country together and strengthening President Hamid Karzai, even as security deteriorated on Sunday in several areas of the country.

In a joint news conference, the NATO commander, Gen. Stanley A. McChrystal, and the senior civilian representative, Mark Sedwill, emphasized that the West supported the peace council, called a jirga, even as many Afghans questioned whether those attending would truly represent the many factions in the country.

“This is a big week for Afghanistan,” said Mr. Sedwill, who described the conference as “the first of a series of major political events that are going to set the agenda of 2010.”

The jirga will be followed by the Kabul Conference on economic development in July and parliamentary elections in September.

“This is a critical moment for this country to bring together all of the people of Afghanistan, their representatives, in an opportunity to set the direction forward and create a national consensus behind the overall approach to security, to development, to reconciliation,” Mr. Sedwill said.

The Electoral Complaints Commission announced Sunday that 85 candidates had been preliminarily barred from participating in the parliamentary elections because they are members of illegal armed groups. They will have the right to appeal. Still, the number is far more than that in the first round of parliamentary elections in 2005, when just 17 people were disqualified for the same reason, according to a former E.C.C. commissioner, Fahim Hakim.

The increase suggests that a more rigorous review system is now in place, analysts say.

Even as the peace efforts proceed in the capital, Kabul, security appeared to be deteriorating in districts in the east and south of the country and on the western border, where Afghan insurgents trained in Iran are returning to fight and smuggling in weapons, General McChrystal said.

“There is clear evidence of Iranian activities, in some cases supplying weaponry and training to the Taliban that is inappropriate,” he said.

In Nuristan Province, on the country’s eastern border, hundreds of local and Pakistani Taliban have taken control of a remote district near the Pakistan border, Barg-e-Matal. The number of fighters who have crossed the border from Pakistan swelled through the week and now has reached 1,000 to 1,500, said Gen. Zaman Mamozai, the commander of the Afghan Border Police for the eastern region of Afghanistan.

They are “mostly from Pakistan and are conducting collective attacks,” he said.

It appears that many of the Taliban from Pakistan had come to Nuristan in search of a new haven after having come under attack from the Pakistani Army in Pakistan. There are few Afghan security troops in Nuristan’s rugged mountains and only a small number of American troops in the province.

NATO leaders say that they cannot control the entire country with the number of troops they have and had to rely on Afghan forces in remote areas. But because not enough Afghans have been trained, NATO officials say they may have to live with some insurgent havens.

“As we execute our strategy and our capacity to secure areas, we must prioritize the order in which we do those, and how we deploy our forces and our assets,” General McChrystal said when asked whether Barg-e-Matal was being allowed to become a sanctuary.

“The Taliban can still muster strength in places and there are a lot of unknowns there,” added a senior NATO officer, speaking about Nuristan on the condition of anonymity because he was not authorized to speak on the record on the matter.

“If there are Taliban there, so what?” he said, adding that the district was far from any population center. He acknowledged that the situation would become more complicated if the Taliban filter out of remote mountain redoubts and into populated areas.

There was violence as well in the southeastern province of Khost, where a barely completed high school, built with international aid, was blown up late Saturday night by men using rocket-propelled grenades and bombs.

The school, which cost $220,000 to build, would have provided classrooms for 1,300 students, said Musa Majrooh, the spokesman for the Khost Education Department. A Taliban spokesman, Zabiullah Mujahid, denied that the Taliban were involved in the blast.

Also in Khost, a suicide car bomber detonated his vehicle at the entrance to the police battalion that patrols suburban areas. Nine police officers were wounded, two of them seriously.

In Nangahar Province, in the east, which until recently was relatively calm, two bombings killed five members of the Afghan security forces, and in Badakhshan Province in the far northeast, six counternarcotics officers were killed when their patrol vehicle was blown up by a homemade bomb.

They were on a mission to eradicate poppy, and the province’s governor, Baz Mohammed, accused narcotics traffickers and the Taliban of setting the bomb.