Pakistan's six-week old coalition government is under threat after former prime minister Nawaz Sharif pulled his party out, citing the coalition's failure to meet Monday's deadline to reinstate 60 judges sacked by the president.

A senior lecturer in international relations at Deakin University, Dr Christopher Snedden, told Radio Australia's Connect Asia program it is a difficult issue because the leader of the coalition partner PPP, Asif Zardari, has "some baggage" in relation to the judicial system.

"He has been charged with various things to do with corruption, and he doesn't want those to be in the public eye," Dr Snedden said.

"Also, it seems that he is wishing to defer to President [Pervez] Musharraf a little bit, which is causing problems."

Mr Sharif, the former prime minister and leader of the PML Nawaz faction, is reportedly keen to restore the judiciary, the pre-November 3 judiciary, because he believes this will sideline General Musharraf.

However the PML-N says it will not go into opposition, and Dr Snedden believes the PPP might look to Mr Musharraf's allies for support.

For the moment both the PML-N and PPP say they will not act against each other, or run against each other in any by-election.

"They certainly are keeping the door open, and apparently when the PML-N withdrew there wasn't a lot of acrimony in it," Dr Snedden said.

"I think it may be a little bit of posturing; it's also the PML-N saying look this is a serious issue.

"They do have this thing called the Murree Declaration in which both the PPP and PML-N agreed that the judges would be restored within 30 days.

"Now that 30 days has passed and I think the PML-N is very keen for that to happen, but the PPP is less keen.

"If they do fall apart then arguably the big winner would be the PML-N because it comes out with its credibility intact, whereas the PPP is going to look like it's less than strong, it will have lost the impetus that it gained in terms of its sympathy vote as a result of Benazir's death, and it will be looking like it's a little bit of a lackey of retired General Musharraf."

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