A senior US envoy has met President Pervez Musharraf to discuss Pakistan's deepening political crisis.
Some opposition supporters did not welcome Mr Negroponte's visit
Diplomats said John Negroponte had delivered a very strong message for an end to Pakistan's state of emergency.
Ahead of the meeting, Gen Musharraf told the BBC his country was safe as long as the military was in charge.
He warned that if polls he has promised for January were held under disturbed conditions, the country's nuclear arms could fall into the wrong hands.
Mr Negroponte, the US Deputy Secretary of State, is expected to try to revive a deal between opposition leader Benazir Bhutto and Gen Musharraf.
He spoke to Ms Bhutto on Friday, saying "moderate forces" should work together to get Pakistan back to democracy.
Mr Negroponte is expected to call for the release of thousands of lawyers and political prisoners and an end of emergency rule as a pre-requisite for a fair election.
But Gen Musharraf had insisted that emergency rule could only be lifted once the security situation in Pakistan improves, a presidential aide said.
"President Musharraf made it clear to the visiting US envoy that the emergency can only be lifted once the situation regarding law and order improves," Gen Musharraf's aide told AFP new agency.
"He told the envoy that the emergency is meant to reinforce and strengthen the law enforcement apparatus in the fight against militancy and extremism," he added.
Mr Negroponte also met General Ashfaq Kiyani, Pakistan's deputy army chief of staff and Gen Musharraf's chosen successor if he resigns as head of the army as promised.
A military official told AFP they had "discussed matters of mutual interest and security".
Gen Musharraf says he will resign as head of the army once the Supreme Court has ratified his next term as president.
In an interview with BBC Radio 4's Today programme Gen Musharraf defended his decision to impose emergency rule.
Diplomats say Mr Negroponte will ask for media curbs to be lifted
He said that if elections were held in the wrong environment, the results could lead to chaos.
And if that happened, he argued, Pakistan's nuclear weapons could become vulnerable.
"They cannot fall into the wrong hands, if we manage ourselves politically... The military is there - as long as the military is there, nothing happens to the strategic assets, we are in charge and nobody does anything with them," he said.
Gen Musharraf told the BBC it was judges and opposition politicians - not himself - who were trying to derail the political and democratic process in Pakistan.
He demanded an explanation for his portrayal in the Western media in recent months.
"Did I go mad? Or suddenly, my personality changed? Am I Dr Jekyll and Mr Hyde?" he asked.
"Have I done anything constitutionally illegal? Yes, I did it on 3 November," he said, referring to his imposition of emergency rule. "But did I do it before? Not once."
"Who is trying to derail the political and democratic process? Am I? Or is it some elements in the Supreme Court - the chief justice and his coterie... and now some elements in the political field?"
Benazir Bhutto was placed under house arrest on Tuesday
Meanwhile two leading independent television channels in Pakistan have been forced to shut down completely.
Cable broadcasts of the stations, Geo and ARY, were stopped when Gen Musharraf imposed emergency rule two weeks ago. But the two channels had been able to broadcast on satellite out of Dubai.
Now the authorities in Dubai have ordered them to stop satellite transmissions.
Angry journalists held a march through the Pakistani city of Karachi, to protest at what they say was direct pressure from Gen Musharraf to shut down the two channels.
The US said the decision to shut the channels down was troubling.
"We are troubled by this expansion of restrictions on the media despite our calls to ease the restrictions," a state department official said.
'Darling of the West'
Gen Musharraf has criticised former Prime Minister Bhutto, despite recent efforts by the two to form an alliance.
He said Ms Bhutto feared the polls, set for January, because she was corrupt and unpopular.
Gen Musharraf said she was "the darling of the West" but that "she would not like to go into an election because her party is not in a state to win at all".
"Therefore, I will certainly go for the election, in spite of any agitation by her. We will not allow her that," he said.
Ms Bhutto, who was released from house arrest on Friday, has said that she will meet other opposition leaders to discuss a boycott of January's assembly elections.
The opposition says polls under emergency rule would lack credibility.