Prime Minister Malcolm Turnbull has urged Labor and the Senate crossbench to back a long-delayed extradition treaty with China that looks likely to be blocked by the Senate.

Key points: Extradition treaty tabled in Parliament earlier this month but human rights group lobbying for it to be dumped

Extradition treaty tabled in Parliament earlier this month but human rights group lobbying for it to be dumped Greens and crossbenchers have backed push to block the treaty, meaning Labor is needed to get it passed

Greens and crossbenchers have backed push to block the treaty, meaning Labor is needed to get it passed PM warns killing off treaty could undermine cooperation between Australian, Chinese law enforcement

The contentious treaty was tabled in Parliament last year, but human rights groups have lobbied for it to be dumped, saying China's legal system has little transparency and no independence.

Newly independent Senator Cory Bernardi has flagged he will try to stop the treaty from being ratified, arguing it would be impossible for Australians extradited to China to secure a fair trial.

The Greens and other crossbench Senators have backed the push to block the treaty, which means its fate rests with Labor.

Mr Turnbull warned that killing off the treaty could undermine cooperation between Australian and Chinese law enforcement agencies.

"The treaty ... needs to be ratified. We are urging the opposition and the crossbenchers to support the ratification," Mr Turnbull said.

"There are very considerable protections in the treaty, and it is an important part of our cooperation with China on law enforcement."

A federal parliamentary committee recommended Australia ratify the extradition treaty in December.

It was signed in 2007 but has never been legislated with some MPs still wary of ratification.

On Monday, the Prime Minister pointed to news that Australian and Chinese authorities had worked together to seize more than 100 kilograms of crystal methamphetamine bound for Australia.

"I just note today yet another very large drug bust, well over $100 million of crystal methamphetamine which has been intercepted which had it not been for that cooperation would have been on the streets in Australia, destroying Australian lives. So that cooperation is very important," he said.

Opposition Leader Bill Shorten said Labor was still weighing up its stance on the treaty.

"We're currently considering this matter very carefully. It is a matter of great importance," he said.

"It goes to questions of our relationship with China [but] it goes though of course to human rights, and it goes to questions of law. Our party will be discussing this matter in the coming days before the vote."

Labor flagged concerns about ratification in a parliamentary report released last year, calling for a review of the extradition act to ensure it is consistent with international legal obligations.

Several sources inside the party have predicted the ALP would decide to back the motion to block the treaty.

Greens Senator Nick McKim said his party would fight to ensure the agreement was never ratified.

"We will not be supporting the extradition of Australians to China so we'll be voting to block that. We've had a look at a number of past cases, we've had a look at the record of the Chinese so-called judicial system over there and we simply don't trust it," Senator McKim said.