Islamabad, Pakistan ? President Gen. Pervez Musharraf yielded to pressure from the United States on Thursday and said Pakistan will hold elections by mid-February. But he showed no sign of ending a political crackdown, sending police to surround the home of opposition leader Benazir Bhutto and detaining thousands ahead of a major protest.

The move against Bhutto today came amid a broader crackdown on her supporters, who were planning to rally near Islamabad against Musharraf’s emergency rule. Bhutto’s party said some 5,000 of its supporters have been rounded up in the last three days, and riot police were out in force in nearby Rawalpindi, the city where today’s rally was to take place.

A security official, who spoke anonymously because he was not authorized to talk to the media, said Bhutto had been place under house arrest. He offered no other details.

Information Minister Tariq Aziz said Bhutto was not formally under house arrest, but “we will not allow any leader to carry out any rally. The law is equal for every body and anyone violating it will be dealt with accordingly,” he told The Associated Press.

On Thursday, the White House hailed Musharraf’s pledge to hold the parliamentary vote, which will come just a month later than originally planned. But Bhutto denounced his announcement as “vague” and demanded Musharraf give up his second post as army chief within a week.

She said the anti-government rally set for today would go ahead despite warnings it could be targeted by suicide bombers. She leads Pakistan’s biggest party and her decision to join in protests was another blow for Musharraf, who has seen his popularity slide this year amid growing resentment of military rule and increasing violence by Islamic militants.

Raja Javed Ashraf, a lawmaker for Bhutto’s Pakistan People’s Party, said today that authorities had arrested 5,000 of its supporters to head off the major demonstration called against emergency rule.

The arrests across the eastern province of Punjab began Wednesday and continued through this morning as police took up positions around Rawalpindi, a garrison city near the capital where Bhutto had planned to address a rally later in the day.

“It is a massive crackdown on our party,” Ashraf said.

Officials publicly offered no immediate comment, but a security official, speaking on condition of anonymity because he was not authorized to talk to the media, said only 1,000 Bhutto supporters had been detained.

On Thursday, in a fourth day of protests against the general’s imposition of emergency rule over the weekend, lawyers rallied peacefully in Islamabad, while demonstrators clashed with police in the border city of Peshawar.

Musharraf has been under increasing pressure to quickly hold elections and resign as army commander since he suspended the constitution Saturday. He said emergency measures were needed to calm political instability he claims is hampering the fight with Taliban and al-Qaida-linked militants.