ISLAMABAD, Pakistan (CNN) -- Pakistan will be under a state of emergency for "as long as it is necessary," Pakistani Prime Minister Shaukat Aziz said Sunday, a day after Pervez Musharraf suspended the constitution and widened his powers as president and military chief.

In a commentary written for CNN on Sunday, opposition leader Benazir Bhutto called Musharraf's plan "a step to entrench his dictatorship" and called for elections under an independent caretaker government.

But Aziz said it could be months before parliamentary elections -- scheduled for January -- will take place.

"The parliament could give itself more time, up to a year, in terms of holding the next elections," Aziz said. "However, at this point, no decision has been made."

The state of emergency had been imposed to "bring more harmony to the pillars of state" and to protect against extremism in the country, Aziz said. See a timeline of the upheaval in Pakistan »

Hundreds of people have been detained.

Earlier in the day, Musharraf's spokesman, Information Minister Tariq Azim Khan, said on Dubai-based GEO TV that parliamentary elections would be delayed indefinitely.

Aziz stressed that despite the emergency measure, Musharraf's government is "committed to pursuing our parliamentary form of government" and "making sure elections are held."

Before imposing the state of emergency, Musharraf had vowed to hold elections no later than January 15.

The move has put the United States in a precarious position and has raised fears about widespread chaos in Pakistan, a nuclear nation.

Washington will review its financial aid package to Pakistan, its key anti-terrorism ally, U.S. Secretary of State Condoleezza Rice said Sunday. Watch Rice call the move to martial law a big problem »

But she noted that the situation is complicated because much of the billions of dollars sent to Pakistan fund anti-terrorism measures.

Washington was not consulted about Musharraf's plan, Rice said, adding that she is "disappointed in his decision."

The political turmoil comes ahead of a Supreme Court ruling on whether Musharraf's recent re-election is legal.

Aziz said there could be "some timing difference" on the schedule for elections but affirmed the Pakistan leadership was still committed to democracy.

Meanwhile, up to 500 people had been arrested so far in a roundup of judges, lawyers and political activists, Aziz said.

About 1,500 are on a list of people to be arrested, according to police sources and witnesses.

Among the political activists arrested is Gen. Hameed Gull, the former head of the ISI, the Pakistani intelligence service, police officials told CNN.

In the wake of Saturday's declaration, the government also issued new rules forbidding newspapers and broadcasters from expressing opinions prejudicial to "the ideology of Pakistan or integrity of Pakistan".

In response to questions on the measures taken by the Pakistan government against the media, Aziz said the media would have to abide by a new "code of conduct."

He insisted that the code was not designed to curb dissent and that "constructive criticism is welcome."

Musharraf declared a state of emergency ahead of a Supreme Court ruling on whether his recent re-election to the presidency was valid.

Bhutto, a former prime minister, said Musharraf is sending the wrong message.

"At a time when he should be demonstrating to our country and the world his seriousness in allowing free, fair and transparent elections, he has declared martial law," Bhutto wrote in the commentary for CNN.

A victory for Bhutto's Pakistan People's Party in parliamentary elections would give her a chance to win a third term as prime minister.

Looking ahead to the next vote, Bhutto urged Musharraf to put in place an "election monitoring mechanism ... that can guarantee the sanctity of the ballot and allows election experts to conduct exit polls to ensure that the counting reflects the voting."

"It is time ... for reconciliation to truly begin that will allow for the mobilization of the moderate majority of my nation and the marginalization of militants, fanatics and extremists," she wrote.

Bhutto, who ended eight years of self-imposed exile when she arrived in Pakistan last month, said Musharraf's declaration probably stemmed from fear that the high court might not certify the October presidential results in which he garnered a vast majority of the votes.

The Supreme Court was considering legal challenges filed by the opposition questioning Musharraf's eligibility to hold office.

"Now, I can understand that he might have had difficulty in accepting the verdict of the Supreme Court, but one has to accept the ruling of a court," she said. Watch Bhutto call the developments in Pakistan a big setback »

Under the constitution, Musharraf was ineligible for run for another term while serving both as president and military leader. However, the court allowed the election to go ahead, saying it would decide the issue later.

Since then, Pakistan has been in a state of political limbo while the Supreme Court tackled legal challenges filed by the opposition that question Musharraf's eligibility to hold office. Some speculated that a declaration of emergency is tied to rumors the court is planning to rule against Musharraf.

Musharraf has stated repeatedly that he will step down as military leader before retaking the presidential oath of office on November 15. E-mail to a friend

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