A day before the Salt Lake City Council is to take up what could be the deciding vote on a countywide $58 million sales-tax hike for roads and mass transit, Mayor Jackie Biskupski tweeted out her opposition to raising the tax now.

“It is not the time for #SLC to support the #SB136 county sales tax increase. I support funding for transportation, but any tax increase should be done after public engagement & with strategic plans, as we have done w/ our local funding options,” she said in a tweet sent just after 5 p.m. Monday.

The Council is scheduled to discuss the tax at its work session beginning at 3:30 p.m. Tuesday and has it on the agenda for a possible vote in its formal session that night.

With a population of around 200,000, the capital could well be the city that either OKs or blocks the proposed .25 percent countywide tax increase.

So far nine cities, representing an aggregate population of more than 400,000 have supported the tax-hike resolution. If cities with a total population of 737,000 residents (67 percent of the total county population of 1.1 million) back the increase, Salt Lake County will implement it.

Salt Lake City Council Chairwoman Erin Mendenhall told The Tribune last week that she believed the countywide tax, which would add a 2.5-cent tax to a $10 purchase, had support from the council because of pressing transportation needs.

Her view didn’t change with the mayor’s statement Monday.

“I think we have a majority, and I think the whole council has been aware of her opposition,” Mendenhall told The Tribune. “I don’t think this is news that will alter the probable support of the resolution, but you never know.”

“We finalize our budget tomorrow and there are all sorts of considerations in the context of that that could play into council members’ consideration of the county resolution. so we shall see.”

Asked if she was surprised Biskupski would go public with her opposition on the eve of a vote, Mendenhall said, “Actually I was surprised she didn’t go public with it earlier.”

The city has long acknowledged the dire state of its roads — with two-thirds of them rated poor or worse. Just Monday, Biskupski held a news conference to tout $5 million in fixes — mostly on the east side.

And in a statement released later Monday, the mayor reiterated her strong support for investing in city streets and transit. But, she added, “I do not believe it is the right time for Salt Lake City to support the quarter-cent sales tax increase currently being considered.”

Biskupski pointed to the recent .5 percent sales-tax hike approved by the city council and mayor — part of which will be used for roads and transit — and a proposed $87 million road bond that could be placed on the Nov. 6 ballot.

“I strongly believe the support the city has received for these funding options exists because of the comprehensive plans we have developed and the robust public engagement we underwent,” the mayor’s statement said.

She contrasted that with the countywide transportation and transit tax proposal, which has only lately begun to see some public scrutiny and debate. A revised version of a 2015 voter-rejected ballot measure, the Legislature authorized it as a county option in March. Then, in April, Salt Lake County decided to leave it up to cities and came up with the 67 percent of population formula, setting a June 22 deadline.

“To fully implement our transit and transportation needs, Salt Lake City will need to think regionally and act locally. Let’s take the time necessary to launch our local plans, and coordinate with our regional partners to fund our future needs in a transparent and strategic manner,” Biskupski urged.