There are moves in Pakistan to restore the sacked former Supreme Court chief justice, Pakistani officials have said.
Pakistan's High Commissioner to the UK, Wajid Shamsul Hasan, told the BBC an announcement was expected soon on Iftikhar Chaudhry's reinstatement.
The move comes as anti-government protesters are planning to march on the capital to demand his reinstatement.
Opposition leader Nawaz Sharif earlier left a police blockade around his home in Lahore to join the protesters.
Riot police had surrounded Mr Sharif's home in an apparent bid to place him under house arrest but the government denied that he was being detained.
The reinstatement of Mr Chaudhry and other judges sacked by former President Pervez Musharraf has been a key opposition demand amid a growing political crisis.
There were clashes as police fired tear gas and baton charged Sharif supporters who threw stones at the police.
Sharif activists later managed to overcome barriers blocking access to the main highway to Islamabad and Mr Sharif left Lahore in a convoy.
Mr Sharif's party, the Pakistan Muslim League (PML-N), has been planning a "long march" to arrive in Islamabad on Monday and demand the reinstatement of judges sacked by former President Pervez Musharraf.
Nawaz Sharif has been a long-term opponent of the President Zardari
Mr Sharif is expected to arrive in Rawalpindi - near Islamabad - later on Monday.
He is due to be joined there by his brother, Shahbaz Sharif, former chief minister of the Punjab, and leaders of the lawyers' movement demanding the judges' reinstatement.
President Zardari, Prime Minister Yousuf Raza Gilani and army chiefs were reported to be holding overnight talks aimed at working out a deal to restore Mr Chaudhry and other judges.
Mr Hasan, Pakistan's chief diplomat in the UK, said the discussion were "in the final stages and some positive announcement will be coming soon".
"There is a move to reinstate all the judges that were dismissed by former President Musharraff and 53 of them were restored by our government and seven were left," he told the BBC.
Mr Chaudhry and 60 other judges were dismissed by Gen Musharraf in 2007. Most have since been reinstated but Mr Chaudhry and a handful have not been allowed to return to their old posts.
The campaign over the judges has become a power struggle between Mr Sharif and President Zardari, says the BBC's Barbara Plett in Islamabad.
The government has arrested hundreds of opposition activists and banned rallies, saying they could trigger violence.
Our correspondent says it is not clear if Mr Sharif will be able to reach Islamabad, given the authorities have blocked routes leading to the capital.
She says the unrest has alarmed the West, which wants Pakistan to focus on the battle against the Taleban on the Afghan border.
The tensions between Mr Zardari and Mr Sharif date back to the 1990s, but the two formed a brief partnership in government after parliamentary elections in February 2008.
President Zardari had promised to bring back the judges when he took office last year following his wife's assassination.
But Mr Sharif's party later left the alliance, complaining of reluctance by Mr Zardari's Pakistan People's Party to reinstate them.
The latest crisis was sparked by a Supreme Court decision to ban Mr Sharif and his brother Shahbaz from elected office, and President Zardari's decision to put their stronghold in Punjab province under direct rule from Islamabad.
Are you in Pakistan? What is your reaction to this news?
Finalmente após os protestos dos advogados e passeatas, o Chefe de Justiça, que realmente fazia justiça voltou ao poder!!!!!!!!!!! Espero que agora a paz volte a reinar. Vamos rezar!