Wally Santana, Associated Press
Supporters of opposition leader Benazir Bhutto are taken away by police as they protest against President Gen. Pervez Musharraf outside of Bhutto's barricaded home in Islamabad, Pakistan Friday.

ISLAMABAD, Pakistan — President Gen. Pervez Musharraf placed opposition leader Benazir Bhutto under house arrest for a single day Friday — surrounding her villa with barbed wire — and rounded up thousands of her supporters to block a mass rally against his emergency rule.

The crackdown dimmed hopes the two pro-U.S. leaders could ever form an alliance. A top American official voiced fears it would obstruct the fight against Islamic extremism — a threat underlined by a suicide bombing in northwest Pakistan that targeted a Cabinet minister, who escaped unharmed.

The U.S. called for the restrictions to be lifted. Hours later, the acting deputy commissioner for Islamabad, Aamir Ali Ahmed, said that they had ended, but her villa remained surrounded by police.

Party members said she would try to leave Saturday morning.

"We'll see tomorrow," said Makhdoom Shah Qureshi, a senior official from Bhutto's Pakistan People's Party as he left a midnight meeting at her home. "You can see for yourself the barriers are still up, the police are still here."

Bhutto twice tried to escape in her car during the day, telling police who surrounded her villa: "Do not raise hands on women. You are Muslims. This is un-Islamic." They responded by blocking her way with an armored vehicle. In nearby Rawalpindi, the city where she had hoped to stage the rally, police tear gassed hundreds of supporters who staged wildcat protests and hurled stones. More than 100 were arrested.

"We remain concerned about the continued state of emergency and curtailment of basic freedoms, and urge Pakistani authorities to quickly return to constitutional order and democratic norms," Gordon Johndroe, a spokesman for the U.S. National Security Council, said in a statement.

Washington, Musharraf's chief international backer, has reason to be worried. Nuclear-armed Pakistan, a country of 160 million, has been wracked by Taliban and al-Qaida-linked violence, including suicide bombings and clashes in its troubled northwest, where insurgents have been gaining the upper hand.

Musharraf cited the spreading militancy as one of the main reasons for the emergency.

On Friday, a suicide bomber blew himself up at the home of Minister for Political Affairs Amir Muqam in the northwestern city of Peshawar. Muqam was unhurt but four others died.

But U.S. Defense Secretary Robert Gates said the political turmoil could undermine the battle along the Afghan border.

"The concern I have is that the longer the internal problems continue, the more distracted the Pakistani army and security services will be in terms of the internal situation rather than focusing on the terrorist threat in the frontier area," said Gates, speaking to reporters on his plane home from a weeklong visit to Asia.

Most of the thousands of people rounded up countrywide since the emergency have been moderates — lawyers and activists from secular opposition parties, such as Bhutto's Pakistan People's Party. The mass detentions have fueled popular discontent and suspicions that Musharraf — who seized power in a 1999 coup — declared the emergency to maintain his own grip on power.

Friday's moves showed that Musharraf has no intention of letting up, despite saying a day earlier that parliamentary elections would go ahead by mid-February, just a month later than originally planned. His announcement came after intense pressure from the United States.

It also further harmed prospects for the Bhutto-Musharraf alliance that Washington has been pushing for.

Speaking to a few dozen supporters inside the barricades after her second foiled attempt to escape, Bhutto said that when Musharraf "suspended the constitution, we suspended our conversation with him."

Her supporters said they would only be further emboldened by Friday's clampdown.

"We are going to besiege" Islamabad, said the Abida Hussain, a former ambassador to the United States. "We will not go away. Our party activists have been mobilized to move out and take to the streets."

Authorities appeared determined to stop them. Bhutto's Pakistan People's Party claimed Friday that 5,000 of its supporters had been arrested in the last three days across the eastern province of Punjab. But security officials said only 1,100 had been detained.

In Rawalpindi, the normally bustling city near Islamabad where Bhutto had planned to hold her rally Friday, hundreds of police — some on horseback, motorcycles or in armored vehicles — kept a tight grip on the largely empty streets and moved fast against any hint of protest.

There were repeated clashes between stone-throwing protesters, who set piles of garbage and tires on fire in the streets, and police, who at times fired tear gas shells from an armored personnel carrier.

Interior Ministry spokesman Javed Iqbal Cheema said authorities had stopped the rally because suicide bombers had gathered in Rawalpindi and Islamabad.

"The rally was stopped only and only because of our security concerns," he said on state-run Pakistan Television.

Associated Press writers Zarar Khan and Stephen Graham in Rawalpindi, Riaz Khan in Peshawar and Munir Ahmad in Islamabad contributed to this story.