Pakistan's parliamentary elections will he held by mid-February, a month later than planned, the country's military ruler said Thursday, a day after US President George W. Bush urged him to hold the vote on time. Opposition leader Benazir Bhutto denounced President Gen. Pervez Musharraf's pledge as insufficient and said he should step down as army chief within a week. With anger over military rule spreading, the United States and domestic opponents are stepping up pressure on Musharraf to end the emergency imposed Saturday, shed his uniform and hold elections as planned in January. Bush, who counts Musharraf as a key ally in the war on terror, telephoned him Wednesday to say he should step down as the military chief and hold the vote on schedule. And Bhutto, a former prime minister who was in talks with Musharraf on forming a post-election political alliance, had added to the pressure by deciding to join protests against the emergency. Authorities reportedly arrested hundreds of her supporters overnight to head off a major rally she is planning near Islamabad on Friday. News that elections would be held by mid-February was flashed on state-run television, which quoted Musharraf as saying the vote would be delayed by not more than one month. The government said earlier this week that the vote could be delayed by as long as a year. Musharraf's decision was announced after a meeting of his National Security Council. The announcement was seen as an indication that the emergency would be short lived because authorities would likely have to ease up on security restrictions to allow campaigning. Attorney General Malik Mohammed Qayyum forecast that the state of emergency would be lifted in "one or two" months. "It depends on how the law and order situation improves," Qayyum told The Associated Press. Musharraf maintains that restoring democracy is his ultimate aim and the emergency was needed to prevent political instability, protect economic growth, and maintain the campaign against extremism and terrorism. 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 the insurgents have in recent weeks scored a series of victories against government forces. Critics, however, say Musharraf, who seized power in a 1999 coup, imposed the emergency measures - suspending the constitution, blacking out independent TV news networks - to maintain his own grip on power. The moves came ahead of a Supreme Court ruling on the legality of his recent re-election as president. Days of protests, most of them by lawyers angered by the attacks on the judiciary, have been quickly and sometimes brutally put down. Thursday was no different. In Islamabad, police chased about 20 high-school students into the city's bar association headquarters after they showed up in solidarity with dozens of protesting lawyers, who were observing the fourth day of a nationwide strike. In Lahore, in eastern Pakistan, more than 100 professors boycotted classes and marched on the campus of the state-run University of the Punjab. Perhaps more troubling for Musharraf, however, has been Bhutto's move to join the protests, adding a new dimension to the worsening political instability. Bhutto pulled back on the talks over a political alliance after the emergency was imposed, saying the president's authoritarian ways have fueled extremism and destabilized the country. She was planning a large protest Friday in Rawalpindi, a garrison city on the outskirts of Islamabad. Authorities appeared determined to keep it from going ahead and about 20 policemen were posted Thursday to keep people out of the park where rally was to be held, Liaquat Bagh - named for Pakistan's first prime minister, who was assassinated there in 1951. The city's police chief, meanwhile, warned that suicide bombers were preparing to attack the rally. "We have intelligence reports that suicide bombers have entered Rawalpindi," said police chief Saud Aziz. He added that the warning was based on specific information and "the situation is very serious." Bhutto's own jubilant homecoming procession last month following eight years in exile was shattered by suicide bombers, leaving more than 145 people dead. Authorities suspect Islamic militants in that attack. With Bhutto showing no signs of calling off the rally - she has repeatedly said she is willing to risk more bombings - police arrested at least 800 of her supporters across the eastern province of Punjab overnight, said Jamil Soomro, a spokesman for the opposition leader. But the government denied the arrests, saying no such crackdown had been ordered. "According to my information, only four members from her party were detained last night when they defied a ban on rallies," said Interior Ministry spokesman Javed Iqbal Cheema. Thousands of lawyers and opposition activists have been detained since Musharraf declared the emergency on Saturday. Four of those arrested were charged with treason Thursday for making anti-Musharraf speeches in the southern port city of Karachi. The men - three politicians from small leftist political parties and a labor union activist - were the first government opponents charged with treason, which carries a maximum penalty of death, since the emergency was imposed. Police in Karachi were also trying to arrest eight lawyers on treason charges for distributing anti-Musharraf leaflets. Bush, personally stepping into the political crisis for the first time, said he told President Gen. Pervez Musharraf in a 20-minute conversation: "You can't be the president and the head of the military at the same time." For days, the White House has faced questions about why Bush was not taking a tougher line against Musharraf who since Saturday's emergency declaration has ousted independent-minded judges, put a stranglehold on the media and arrested thousands of mainly moderate, secular Pakistanis. "My message was very plain, very easy to understand, and that is, the United States wants you to have the elections as scheduled and take your uniform off," Bush said during a news conference with French President Nicolas Sarkozy in the U.S. state of Virginia. A Pakistani Foreign Ministry statement said Musharraf, a key US ally in its war on terrorism, had told Bush he "was committed to full democracy and civilian rule in the country as he had promised to the people of Pakistan."