ISLAMABAD — A political dogfight in Pakistan is delaying efforts to secure treatment overseas for ailing ex-prime minister Nawaz Sharif, whose health remains "critical" according to his doctor on Friday.

Pakistani courts have granted bail to Sharif — who is serving a prison sentence for corruption — so that he may seek treatment and Islamabad had previously said it would not block requests to remove him from a travel ban list.

This week, however, the government of Sharif's rival Imran Khan added a condition to his travel, saying he must pay a bond of seven billion Pakistani rupees ($45 million) — which Sharif's party, the Pakistan Muslim League-Nawaz (PML-N), immediately rejected.

"Former PM #NawazSharif's health status remains critical," his doctor Adnan Khan tweeted Friday. "The delay could've serious adverse health & life consequences."

"We... want to make it clear that, God forbid, if something happens to Sharif, the party will hold Imran Khan responsible," the PML-N's current leader, Sharif's brother Shahbaz Sharif, said in Islamabad on Thursday.

The party has petitioned the Lahore High Court seeking an unconditional end to Sharif's travel ban.

Sharif, Pakistan's longest-serving premier, was ousted from his third term in office in 2017 and later jailed on corruption charges.

His health deteriorated while in prison and he suffered a minor heart attack last month, his party said, while his doctor Adnan Khan claimed on Twitter that the ex-leader was "fighting for his life".

He was bailed last month and briefly hospitalized before being taken to an intensive care unit set up at his home outside the eastern city of Lahore.

Sharif, who is suffering from an autoimmune blood disorder, also has high blood pressure and his kidney functions are deteriorating, according to aides.

They have said the unexplained cause and uncertain diagnosis require advanced investigations and specialised care.

The prime minister has said several times that he will not seek to use Sharif's illness for political gain.

Dawn, an English-language newspaper, pointed out that there was no legal reason for the additional bond.

"A normal situation which could have been handled normally has now turned into a full-blown crisis," the newspaper's editorial noted Friday.

"(T)he former prime minister needs urgent and immediate treatment abroad. In such a situation, the government's callous decision to demand an indemnity note smacks of political point-scoring and one-upmanship... The result is an acrimonious fight that is eating away precious time."

Sharif, known as the "Lion of Punjab", is a political survivor who has repeatedly roared back to the country's top office. The 69-year-old served three terms — but did not complete a single one.

His first, beginning in 1990, ended in 1993 when he was sacked for corruption. The second lasted from 1997 to 1999, when he was deposed by the powerful military.

Sharif blamed the security establishment for again targeting him in 2017 when the Supreme Court disqualified him from politics for life over graft allegations, which he denies. He was later jailed. — AFP