CANBERRA, Australia - Vote counting resumed Tuesday in Australia's dramatically close national election, three days after the contest failed to deliver an immediate winner and left the nation's leadership in doubt. But with officials warning that the victor may not be known for days, if not weeks, many were left wondering: What, exactly, is taking so long?

Counting was suspended in the early hours of Sunday morning while the ballot papers were secured and catalogued in a bid to avoid a repeat of a fiasco in 2013 when the mislaying of 1,370 ballot papers forced a re-run of the Senate election in Western Australia state.

Authorities have to wait until 13 days after the July 2 election date for the final mail-in votes to arrive. The Australian Electoral Commission said 400,000 of an expected 1.5 million postal votes had yet to arrive by Tuesday.

With about a quarter of the votes left to be counted, neither Prime Minister Malcolm Turnbull's conservative Liberal Party-led coalition nor opposition leader Bill Shorten's centre-left Labor Party had won the 76 seats in the 150-seat House of Representatives needed to form a government - raising the prospect of a hung parliament.

"I know many Australians find this sort of frustrating, the wait. And you can imagine that we are among them," Turnbull told reporters with a laugh. "We would like to get a clear result on Saturday night. But the truth is that we've had long waits before. Many times actually, over the years. And in many countries, many other countries, similar western democracies, it takes a long time to determine the outcome of an election."

David Glance, director of the University of Western Australia's Center for Software Practice, said the political standstill demonstrated a need for online electronic voting.

While many countries vote with a ballot paper and pencil, Australia is a special case because compulsory voting led to extraordinarily large voter turnouts. Plus Australian politics had become more volatile, with bigger swings and more alternative candidates to the major parties, Glance said.

Australia's complex unique voting system, in which voters rank candidates in order of preference, also made calculating winners more labour-intensive. And Australia has had recent experience in lost ballot papers.

"There's this political uncertainty which can last for days and weeks, and potentially now we've moved into a phase where this is going to become more the norm than the exception," Glance said.

As of Tuesday, Australian Broadcasting Corp. election analysts - considered among the most reliable - were predicting that the coalition had 68 seats, Labor 67 and the minor parties and independents were leading in five seats. Another 10 seats were in doubt.

While hung parliaments are rare in Australia, the last occurred at an election only six years ago. Key independents then took 17 days from the election date before declaring they would support a Labor minority government which became chaotic and unpopular. It was wiped out in a landslide election in 2013.

Delays in determining election results are, of course, not unprecedented on a global scale. The notoriously close 2000 U.S. presidential election pitting Republican George W. Bush against Democrat Al Gore led to a recount in the state of Florida, where problems with ballot machines led to confusion over who voters had actually selected. The results were in doubt for weeks until a ruling by the Supreme Court led to Bush being declared the winner.

Turnbull, who became prime minister 11 months ago because his predecessor was unpopular, said Tuesday that he would not take Shorten's advice by resigning as British Prime Minister David Cameron did over Britain's decision to leave the European Union.

"The count is continuing and we remain confident that we will secure enough seats to have a majority in the parliament," Turnbull told reporters.

Shorten, who could become Australia's s fifth prime minister in three years, said Turnbull had "promised stability and taken Australia on a roller coaster ride."

"He wanted a mandate for stability and he's given us instability," Shorten said.

The makeup of Australia's Senate is likely to take even longer than the House of Representatives to determine. But early signs are that the Senate will be even more unwieldy for whichever party takes government.

Early projections suggest that if the conservatives retain power, they would need the support of eight of 10 crossbenchers to pass contentious bills. These crossbenchers would include senators who oppose the government's free trade agenda and nondiscriminatory immigration policy and could demand concessions in these areas.

Ratings agencies fear the Senate could threaten Australia's chances of balancing its books by 2020-21 by blocking tough savings measures and therefore also threaten its rare AAA credit rating.

"Fitch views Australia's overall credit profile as still consistent with a 'AAA' rating, but political gridlock that leads to a sustained widening of the deficit would put downward pressure on the rating, particularly if the economic environment deteriorates," Fitch Ratings said.

"Irrespective of the political composition of any new government, we would lower the rating if the parliamentary gridlock on the budget continues and Australia's budgetary performance does not improve broadly as we expected a year ago," Standard & Poor's said.

Australian Electoral Commission spokesman Evan Ekin-Smyth said the Senate was likely to take a month to resolve. He said the House of Representatives would not take as long, but he could not give a more specific estimate.