Government sources have told media that Prime Minister Scott Morrison will not call an election on Sunday, which had been widely anticipated.

Sunday was the most likely choice if Morrison were to opt for the first of three dates available to him — May 11, May 18 and May 25. While many commentators had previously thought May 11 the most likely election date, May 18 would give the ruling coalition another week to use government money to advertise its policies and achievements.

Once an election is called, the coalition becomes a caretaker government and would need the approval of the center-left Labor Party opposition if taxpayers were to continue funding of what are described as government public information campaigns.

The government is trailing Labor in opinion polls.

Prime ministers traditionally call elections on a Sunday. The campaigns last at least 33 days and officially start a few days after the date is announced.

Monday is the last day that Morrison can call a May 11 election. But doing that would mean senators who had flown to the Australian capital Canberra for committee hearings starting Monday would be sent home that day.

The Australian Electoral Commission website says May 18 is the last possible date for the election because counting votes can take six weeks and must be finalized by June 30. The government would have to invest in more commission resources to cope with a tighter deadline created by a May 25 election.

But Treasurer Josh Frydenberg, the deputy leader of Morrison's conservative Liberal Party, said on Sunday that May 25 remained an option.

Morrison has maintained that he would call an election sometime after April 2 when Frydenberg announced the government's annual budget plan for the next fiscal year beginning July 1.

The government plans to deliver Australia's first surplus budget in 12 years. Labor also promises to balance the budget next year, but had yet to detail how.

Frydenberg said his government was using the time before an election is called to continue explaining its budget plan.

"There's no haste. There's no delay," Fydenberg told Australian Broadcasting Corp., referring to the election timing. He declined to say how money would be spent on government advertising this week, saying that figure would be made public at a later date.

"Money is being spent in accordance with approved processes and that's all transparent," he added.

Prime ministers usually keep their choices of election dates a tightly guarded secret in an effort to put the opposition at a tactical disadvantage.