WASHINGTON (AP) — President Donald Trump has scrapped the tax plan he campaigned on and is going back to the drawing board in a search for Republican consensus behind legislation to overhaul the U.S. tax system.

The administration's first attempt to write legislation is in its early stages and the White House has kept much of it under wraps. But it has already sprouted the consideration of a series of unorthodox proposals including a drastic cut to the payroll tax, aimed at appealing to Democrats.

Some view the search for new options as a result of Trump's refusal to set clear parameters for his plan and his exceedingly challenging endgame: reducing tax rates enough to spur faster growth without blowing up the budget deficit.

Administration officials say it's now unlikely that a tax overhaul will meet the August deadline set by Treasury Secretary Steve Mnuchin. But the ambitious pace to figure out a plan reflects Trump's haste to move quickly past a bruising failure to broker a compromise within his own party on how to replace the health insurance law enacted under President Barack Obama.

The White House is trying to learn the lessons from health care. Rather than accepting a bill written by the lawmakers, White House officials are taking a more active role. Administration officials have signaled that they want to pass tax legislation with only Republican votes, yet they've also held listening sessions with House Democrats.

White House aides say the goal is to cut tax rates sharply enough to improve the economic picture in depressed rural and industrial pockets of the country where many Trump voters live. But the administration so far has swatted down alternative ways for raising revenues, such as a carbon tax, to offset lower rates.

Trump, who brands himself as a deal-maker, has not said which trade-offs he might accept and he has remained noncommittal on the leading blueprint, from Rep. Kevin Brady, chairman of the Ways and Means Committee.

Brady, R-Texas, has proposed a border adjustment system, which would eliminate corporate deductions on imports, to raise $1 trillion over 10 years that could fund lower corporate tax rates.

But that possibility has rankled retailers who say it would lead to higher prices and threaten millions of jobs, while some lawmakers have worried that the system would violate World Trade Organization rules.

Brady has said he intends to amend the blueprint but has not spelled out how he would do so.

Other options are being shopped on Capitol Hill.

One circulating this past week would change the House Republican plan to eliminate much of the payroll tax and cut corporate tax rates. This would require a new dedicated funding source for Social Security.

The change, proposed by a GOP lobbyist with close ties to the Trump administration, would transform Brady's plan on imports into something closer to a value-added tax by also eliminating the deduction of labor expenses. This would bring it in line with WTO rules and generate an additional $12 trillion over 10 years, according to budget estimates. Those additional revenues could then enable the end of the 12.4 percent payroll tax, split evenly between employers and employees, that funds Social Security, while keeping the health insurance payroll tax in place.

This approach would give a worker earning $60,000 a year an additional $3,720 in take-home pay, a possible win that lawmakers could highlight back in their districts even though it would involve changing the funding mechanism for Social Security, according to the lobbyist, who asked for anonymity to discuss the proposal without disrupting early negotiations.

Although some billed this as a bipartisan solution, and President Barack Obama did temporarily cut the payroll tax after the Great Recession, others note it probably would run into firm opposition from Democrats who are loathe to be seen as undermining Social Security.

The White House would not comment on the plan, but said a value-added tax based on consumption is not under consideration "as of now," according to a White House statement.

The lack of detail about how to significantly rewrite tax laws for the first time in 30 years may provide Trump some time to build consensus among Republicans. But without Trump laying down his hand, lawmakers appear reluctant to back a plan that will likely stir controversy.

"Because there are trade-offs, congressmen need cover from the president to withstand the lobbyists and constituents who are going to complain," said Bill Gale, an economist at the Brookings Institution who worked at the White House Council of Economic Advisers during President George H.W. Bush's administration.

The Trump administration appears to have shut out the economists who helped assemble one of his campaign's tax overhaul plans, which independent analyses show would have increased the budget deficit.

"It's a little frustrating that they feel they have to write a new tax plan when they have a tax plan," said Steven Moore, an economist at the conservative Heritage Foundation who helped formulate tax policy for the Trump campaign.

Sen. Rob Portman, R-Ohio, a member of the Senate Finance Committee, said that all of the trial balloons surfacing in public don't represent the work that's being done behind the scenes.

"It's not really what's going on," Portman said. "What's going on is they're working with on various ideas."

Investors are beginning to show some doubts that Trump can deliver. Stocks rallied after his election on the promise of lower taxes and fewer regulations, but the Dow Jones Industrial Average has dipped 1.2 percent over the past month as the path for health care and tax revisions has become muddied.

"The White House is going to need its own clear direction, or it's going to need to defer to Congress, but saying that your plan is forthcoming and then not producing a plan kind of puts everything in stasis," said Alan Cole, an economist at the conservative Tax Foundation.