By Rob Taylor

CANBERRA, April 9 (Reuters) - Australia's government has been thrown a lifeline in its fight to win backing for an ambitious super-fast national broadband, with opponents split over the plan and one tipping it will pass an obstructive parliament.

Prime Minister Kevin Rudd has promised to build a A$43 billion ($30.5 billion) private-public broadband network over eight years, which would be the country's largest infrastructure project, if it survives political opposition. [nSYD424635]

The major conservative opposition party has criticised the plan, but the leader of its junior coalition partner in the upper house Senate said while he would seek changes, the parliament would ultimately back Rudd's vision later this year.

"My first choice of action would be to try and stop it so we don't get ourselves into an outrageous amount of debt, but I'll have to be a realist. That is not going to happen," Nationals Senate Leader Barnaby Joyce told state radio.

Rudd's centre-left government needs the backing of five Australian Greens senators and two swing-vote independents to massage laws through an upper house dominated by the conservative Liberal-National coalition controlling the largest voting bloc.

"The Greens will you know dance around the edges and say yes, and the independents will you know end up saying yes, so it will go through," Joyce predicted.

He said the A$43 billion broadband plan was outrageously expensive, with the government having already promised A$78 billion in stimulus measures since last September in a bid to shield the economy from an expected recession.

Labour data out later on Thursday is expected to show Australia lost a net 25,000 jobs in March, pushing unemployment to a 4-½ year high of 5.4 percent and keeping pressure on policymakers for more monetary and fiscal stimulus.

Joyce, whose party draws most support in Australia's far-flung regions, said he would seek to ensure regional people are looked after, as Rudd's plan covered only the 90 percent of the country's 21 million population who live in cities and towns.

Australia has slower and more expensive Internet services than many developed countries, raising concerns about competitiveness, but the project will be made more difficult by the country's vast distances and inhospitable terrain.

With the government needing to raise A$20 billion in private investment and more from the sale of bonds to the public, Treasurer Wayne Swan said the government contribution would not be close to the full A$43 billion project cost.

The leader of the major opposition Liberal Party, Malcolm Turnbull, received another setback in his criticism of Rudd's plan on Thursday with senior Liberal leaders in two states backing the government.

Tasmania state opposition leader Will Hodgman and Western Australia Treasurer Troy Buswell supported Rudd's plan to spend more than A$21 billion of taxpayer funds to build a broadband network 100 times faster than existing services, the Australian newspaper said.

($1=A$1.40) (Editing by Jerry Norton)