Australia's parliament is moving toward a vote as early as Thursday on changes to immigration law that would allow a proposed refugee swap with Malaysia to go forward.

Analysts give the bill little chance of passage in the face of opposition from the right-wing Liberal Party and the left-wing Greens, whose support keeps Prime Minister Julia Gillard's minority Labor Party in power.

Ms. Gillard proposes to send 800 undocumented asylum seekers to be detained in Malaysia while their applications are processed. But Australia's high court has blocked the plan, largely because of Malaysia's failure to sign a U.N. convention on the treatment of refugees.

The legislation before parliament would remove the obstacles to the swap plan, under which Australia would accept 4,000 processed refugees from Malaysia.

But Liberal leader Tony Abbott says his party will vote against the bill, arguing it is inhumane to send refugees to be held in Malaysia. He would prefer to re-open a detention camp on the Pacific island of Nauru, where asylum seekers were held when the Liberals were in office.

Labor closed the camp in Nauru on humanitarian grounds when it came to office, but the Nauru government has since signed the U.N. convention on refugees.

Both Australian parties argue that offshore processing of refugees will discourage asylum seekers from using the services of people traffickers who try to transport them across the ocean to Australia in often unsafe boats.