"I came to the university to lead a rally of students against the dictator Musharraf and his illegal actions," Khan said.
 
"I would have presented myself for arrest in full public view, but my goal was to set in motion a student movement."
 
Khan said a group of students from the hardline Jamaat-e-Islami party had collaborated with the police to arrest him.
 
Khan had been in hiding for 12 days after Musharraf declared emergency rule.
 
US mission
 
Khan's arrest came after the US said it was sending its number two diplomat to Pakistan to urge Musharraf to end emergency rule.
 
John Negroponte, the US deputy secretary of state, is expected during his visit on Friday to push for a return to constitutional rule and for free and fair elections to be held.
 
Special report

The move comes amid upheaval in Pakistan following the imposition of a state of emergency by Musharraf in early November, leading to the suspension of the constitution, sacking of the chief judge and a crackdown on the media.
 
Tom Casey, the US deputy state department spokesman, said on Wednesday: "I would expect that he will provide the same message in private to Pakistani officials that we have been saying in public.

"We want to see all moderate political forces be able to work together. We continue to want to see elections move forward in a free, fair and transparent manner [and] we want to see the emergency decree lifted."

Opposition alliance

In a separate development, the leaders of Pakistan's two main opposition parties are reported to be working to form an alliance.

The proposed pact was revealed by Benazir Bhutto, a former prime minister and head of the Pakistan Peoples' Party, who remains under house arrest in her Lahore residence.

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"I am very worried and angry - Musharraf should realise that we don't need him"
 
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Bhutto has called on Musharraf to step down as president and said she is seeking a partnership with Nawaz Sharif, her long-time rival and the exiled leader of the Pakistan Muslim League.

She said: "[Musharraf] must quit as president and as chief of army staff.
 
"I call on the international community to stop backing ... the man whose dictatorship threatens to engulf this nuclear-armed state in chaos," she said.
 
She also said for the first time that she would not serve under Musharraf should he win the elections he has promised by January 9.
 
"I would not serve as prime minister under a man who has repeatedly broken his promises, who is a dictator," said Bhutto, who has previously held talks with Musharraf on sharing power.

On Wednesday, Sharif said he was ready to work with Bhutto, against Musharraf.
 
"We are ready to set aside our differences with the People's Party and work for the return of democratic rule," Sharif said by telephone from Saudi Arabia, referring to Bhutto's party.
 
Asked whether there was any possibility of a broad opposition coalition against Musharraf, Sharif said: "It's the need of the hour."

Defiant Musharraf
 
Musharraf rejected Bhutto's call to resign as well as an appeal by Condoleezza Rice, the US secretary of state, to lift the state of emergency.

"I totally disagree with her," Musharraf said of Rice in an interview in Islamabad with The New York Times.

"The emergency is to ensure elections go in an undisturbed manner."

The Pakistani president has insisted emergency rule is necessary, saying: "The emergency contributes toward better law and order and a better fight against terrorism."

The country has seen increasing violence this year since government forces cracked down on vigilante fighters and students at Islamabad's Red Mosque and a peace treaty with tribal elders in the mountainous regions bordering Afghanistan fell apart.

Local media on Wednesday reported that tribal fighters following religious leader Maulana Fazlullah had expanded their control of a mountain valley in north-western Pakistan.

About 400 armed men took control of the town of Alpurai late on Tuesday in the Swat valley, where fighters have battled government troops since July, The News daily said.