Thousands of Pakistanis, joined by a group of US anti-war activists, headed toward Pakistan's militant-riddled tribal belt on Saturday, to protest US drone strikes – even as a Pakistani Taliban faction warned that suicide bombers would stop the demonstration.

The motorcade march was led by Imran Khan, the former cricket star turned populist politician who heads the Pakistan Tehreek-e-Insaf party. Militants have dismissed Khan as a tool of the West despite his condemnations of the drone strikes, which have killed many Islamist insurgent leaders.

Pakistanis in small towns and villages along the 250-mile route warmly welcomed the convoy, which included more than 150 vehicles. Footage broadcast on Pakistani television showed people showering rose petals on the motorcade. But by late Saturday, it appeared increasingly less likely the protesters would reach the South Waziristan tribal area, where they hoped to stage a major rally.

Government officials had warned of dangers in South Waziristan, which is a frequent focus of drone strikes and was the scene of a 2009 Pakistani army offensive. Pakistani media reported authorities used shipping containers to block the main road leading into the region, where access has long been heavily restricted.

In an interview with the private Dunya TV channel, Khan said he had reached another major town on the route, Dera Ismail Khan, and that he would consult with his party leaders on the situation. The protesters had planned to stay overnight in the Dera Ismail Khan area before heading to South Waziristan on Sunday.

"We have come here for peace," Khan said. "I don't want to put the life of my guests in danger, but I would like to know the level of the threat."

Around three dozen Americans from the US-based anti-war group CODEPINK joined the march. Foreigners are normally forbidden from entering Pakistan's tribal regions.

The American protesters echoed Pakistani condemnations of the US drone strikes, saying that contrary to the claims of American officials, the strikes have terrorized peaceful tribes living along the Afghan border and killed many innocent civilians, not just Taliban and al-Qaida fighters.

"I'm hoping that what [the protest] will show is that the Pakistani people and American people and even the people in the tribal areas want peace," said Joe Lombardo, a US activist from Delmar, New York.

James Ricks, another American, said he was going along with the convoy despite the danger. "I am taking this risk because my government is committing international war crimes and we want to stop this," said Ricks, of Ithaca, New York.

Khan, in brief chats with media at different stops, said government officials had tried to discourage people from joining the march.

"Fearing this will be an historic rally, they [the government] have attempted to discourage people through scare tactics but you have seen the response," he said. "This will prove to be a historic event."

Khan has seen his popularity surge in recent years in Pakistan, where the government, led by the Pakistan People's Party of Asif Ali Zardari, has disappointed many. The former cricketer, who captained Pakistan when they won the 1992 World Cup, had long had a reputation as a playboy. But in recent he has said he has grown stronger in his Muslim faith. He also has used attacks on the US drone program as a means of gaining public esteem in Pakistan.

The main faction of the Pakistani Taliban, which is based in South Waziristan, issued a statement Friday calling Khan a "slave of the West" and saying that the militants "don't need any sympathy" from such "a secular and liberal person".

The statement did not reveal anything about the militants' plans regarding the march, but added: "Imran Khan's so-called Peace March is not in sympathy for drone-hit Muslims. Instead, it's an attempt by him to increase his political stature."

On Saturday, a statement from a Taliban faction said to be based in Pakistan's eastern Punjab province warned that militants would welcome the protesters with suicide bombings.

"We ask the brave people of Waziristan not to side with the gang of Jews and Christians – otherwise their fate will be terrible," the Punjabi Taliban said in the statement.

Khan iattacked the militant accusations. "We have no political aims but want to protect tribal people from drone attacks," he said. "They are whispering that Jews and Christians are coming. They should feel shame for this act."

Earlier in the week, Khan alluded to the possibility that entering South Waziristan might not be possible. He said the demonstrators would go as far as they could, then stage a major rally wherever they decided to stop.