* Australia leader plans May 3 Budget
* Expects election to be held on July 2
* Move is intended to clear deadlock in hostile Senate (Adds Turnbull quotes, election campaign specifics)
SYDNEY, April 19 (Reuters) - Australian Prime Minister Malcolm Turnbull said on Tuesday that the country would probably go to the polls on July 2, after parliament voted down a key labour reform bill, paving the way for an unusually long election campaign.
Turnbull announced the measure a day after the Senate blocked his government's proposal to reinstate a building industry regulator.
The bill was widely expected to fail after opposition lawmakers depicted the proposed watchdog as an attack on unions. But Turnbull pursued it nonetheless as he had sought a reason to call an election.
Sticking to a timetable that he flagged last month, Turnbull told reporters his conservative government will function as normal until May 3, when it will deliver its budget.
"My intention is, an appropriate time after the budget has been delivered, I will be asking the governor-general to dissolve both houses of the parliament for an election which I expect to be held on the second of July," Turnbull said.
Under the Australian constitution, if the parliament was dissolved Turnbull would not be able to deliver a budget, something he wants to do to shore up his popularity both in the electorate and within his party.
"We have all of that work ahead of us, and we will be doing all of that and making a lot more decisions between now and when I expect both houses to be dissolved," he said, referring to the budget.
Turnbull is using the rare "double dissolution" manoeuvre - only possible in Australia after a bill has been rejected by the Senate twice - to revamp a Senate dominated by a host of unaligned minor parties and the main centre-left Labor party.
The move also gives Turnbull a chance to reassert his leadership after ousting former leader Tony Abbott in a party room coup in September. Since then, Turnbull's once-considerable lead in opinion polls has been in decline.
An election campaign effectively lasting 74 days, more than double the conventional five-week duration in Australia, will add to a sense of instability that has been haunting the country's Federal politics for half a decade.
Before Australia's last general election in 2013, another former prime minister, Julia Gillard, announced a September poll date in January of that year, more than 200 days in advance.
If Turnbull loses on July 2, Labor opposition leader Bill Shorten will be the country's sixth leader since 2010.