Prime Minister Sanae Takaichi is pitching a two-year break on Japan’s 8 percent sales tax rate for food, but has yet to show investors a credible way to pay for it without borrowing, reviving fears of a market backlash similar to the one that engulfed former UK leader Liz Truss.

The proposed pause of the levy on food and non-alcoholic beverages is expected to cost roughly 5 trillion yen ($31.6 billion) per year, according to the Finance Ministry — not much less than the total amount spent on education, science and culture combined. Takaichi has sought to reassure markets that she can cover the bill without issuing additional deficit-financing bonds, but hasn’t explained what alternative revenue would fill the gap. That’s resulted in a meltdown in the Japanese bond market as investors worry over the country’s already massive debt burden.

“It remains highly uncertain whether the consumption tax cut can be implemented without relying on government bond issuance,” said Ataru Okumura, a senior interest-rate strategist at SMBC Nikko Securities.

Takaichi seems to have bet that the tax cut will help her consolidate power in an election next month by addressing inflation, a top voter concern. But she faces a tricky balancing act of wooing voters while reassuring the market that her spending pace won’t get out of hand.

Japan’s 40-year bond yield hit 4 percent Tuesday, the highest since its debut in 2007 and a first for any maturity of the nation’s sovereign debt in more than three decades. Investors have been dumping Japanese bonds as speculation grows Takaichi’s party will win more seats and consolidate her power, giving her a freer hand to boost stimulus.

“Historically Japanese administrations have underestimated the risks of rising interest rates and yen depreciation from expansionary policy,” said Prashant Newnaha, a senior Asia-Pacific rates strategist in Singapore. “Markets are beginning to price this risk via higher neutral rates and higher term premiums and hence the absence of buyers in the JGB market.”

Takaichi announced the temporary tax cut proposal on Monday to woo voters ahead of a Feb 8 lower-house election, but the measure could become permanent given the difficulties past governments have faced in raising the sales tax. Japan will hold an upper-house election in the summer of 2028, which is likely to increase political pressure to extend the food sales tax cut to keep voters satisfied.

“Markets are becoming more conscious of fiscal expansion,” said Takuya Hoshino, chief economist at Dai-ichi Life Research Institute. “They are finding it harder to buy when they worry about a possible acceleration of expansionary fiscal policy going forward.”

Meanwhile, Japan’s largest opposition bloc is calling for the permanent elimination of the food sales tax — arguably taking a stance that’s less fiscally cautious. The Centrist Reform Alliance aims to achieve the change by managing a sovereign wealth fund to generate financing, though details of the mechanism remain unclear.

Other parties’ suggestions cost even more. The Democratic Party for the People is arguing for a cut to the overall sales tax to 5 percent from the current 10 percent until real wages turn positive in a sutainable manner, which would cost 15 trillion yen, while right-wing newcomer Sanseito is proposing eventually cutting all sales tax to 0 percent — a move similar in scale to Truss.

Still, by one measure, Japan has more fiscal room to expand Takaichi’s pro-growth economic agenda through additional spending, as nominal growth has picked up thanks to inflation, substantially lowering the debt-to-GDP ratio. Takaichi’s tax cut plan is also worth less than 1 percent of GDP — significantly less than Truss’s proposal, which equated to the biggest tax cuts in half a century and ultimately brought down her government in a matter of weeks.

As parties jostle over tax cuts to lure voters, inflation has already been increasing Japan’s tax revenue. SMBC Nikko’s Okumura estimates the annual revenue boost would be more than 2 trillion yen, while government interest payments on the debt burden would also rise by around 2 trillion yen. That means only part of the additional tax revenue could be used for economic measures, falling far short of the 5 trillion yen needed for the food sales tax cut.

“New funding sources must be secured, or else the bulk of the funding will need to rely on new government bond issuance,” Okumura said.

Japan’s Growth Strategy Minister Minoru Kiuchi tried to reassure markets Tuesday, saying that the Takaichi administration would keep fiscal discipline in mind as it considers the tax cut. Non-tax revenue and a review of excess spending are among the options to fund it, he said, adding that the government will keep bringing down the debt-to-GDP ratio.

“We’ll continue to watch market moves with a high sense of urgency,” said Kiuchi. “We’ll keep up efforts to maintain market trust.”