Pakistan's beleaguered premier said Monday he would appear in court to face a contempt notice served on him for failing to re-open corruption cases, amid a crisis likely to force early elections.

The Supreme Court found Prime Minister Yousuf Raza Gilani in contempt and summoned him later this week, escalating pressure on a weakened government at a time of crippling tensions with the army which some analysts believe could cost the PM his job.

The court wants the government to write to Swiss authorities to demand they re-open corruption cases against President Asif Ali Zardari after an amnesty expired in late 2009.

Judge Nasir-ul-Mulk on Monday told the Supreme Court, which met to debate how to proceed on graft charges against Zardari, that Gilani had been ordered to appear before it on Thursday

Gilani agreed to the summons in the National Assembly late Monday, after his ruling Pakistan Peoples Party (PPP) and its coalition partners passed a resolution expressing full support for democracy and democratic institutions.

"The court has summoned me and I will appear before it as a mark of respect on January 19," he said in an address televised by Pakistani TV channels.

"There can be difference of opinion with the judiciary and the military but they cannot either pack up or derail the whole system. Rather, they have to strengthen it."

"We have struggled for democracy," he said, adding: "We have to strengthen the parliament and democratic institutions."

As the resolution was put to vote, the main opposition party, Pakistan Muslim League (Nawaz) walked out of the house, with its leader in the assembly, Chaudhry Nisar Ali calling it a "smokescreen".

After days of high tension between the military and civilian leadership, the resolution insisted "all the state institutions must strictly function within the limits imposed on them by the constitution" and Pakistan's well-being should be ensured through democratic institutions.

Zardari and the PPP leadership insist the president is immune from prosecution as head of state and Maula Bakhsh Chandio, minister for law and parliamentary affairs, said they would take legal advice on how to proceed.

In the past, the PPP has accused the judiciary of overstepping its reach and colluding with the army to bring down the administration before its five-year mandate ends in 2013.

Last year, a Swiss prosecutor said that it would be "impossible" to reopen a case against Zardari, as he has immunity.

Supreme Court judges have outlined six options on how to proceed on graft charges against Zardari -- which include finding Gilani in contempt, disqualifying the prime minister and president, and holding early elections.

Mulk said he had been left with "no option" but issue the notice to Gilani after the government ignored the court's demands.

It is only the second time that contempt of court proceedings have been initiated against a serving prime minister in Pakistan.

In November 1997, prime minister Nawaz Sharif was also found in contempt in a case which ultimately led to the resignation of president Farooq Leghari.

Analysts are divided on whether Gilani could be convicted, pushed out to protect Zardari or show flexibility in order to avert a wider crisis.

"There is possibility now that the prime minister will be made a scapegoat and he may resign," senior lawyer Quosen Mufti told AFP.

"Another possibility is that the prime minister will appear before the court... If he gives the court a commitment on implementation the court can discharge the contempt notice. If not then he may be convicted."

Zardari's government is also under pressure over a memo soliciting American help to prevent a coup apparently feared in the aftermath of Osama bin Laden's killing in Pakistan in May.

A close Zardari aide, Husain Haqqani, was forced to resign as ambassador to Washington and the Supreme Court ordered a judicial inquiry into the memo following a demand from the chief spymaster.

The army has carried out three coups in Pakistan, but analysts believe it has no appetite for another direct takeover, instead preferring to force early elections behind the scenes in concert with pressure from the courts.

The attorney general said Monday he had been unable to obtain crucial evidence -- BlackBerry message data between Haqqani and US businessman Mansoor Ijaz, who claims to have acted as a go-between on the memo.

He said BlackBerry's makers refused to release such records without the customer's permission.

The commission adjourned the hearing until January 24.