Japan plans to use what are known as bridging bonds to help finance Prime Minister Sanae Takaichi’s investment plans, the government’s top spokesperson said, a development that comes as investors are already concerned about more debt issuance.

“Japan has implemented multiyear budget measures through the issuance of bridging bonds backed by funding sources,” Chief Cabinet Secretary Minoru Kihara told reporters Thursday, citing previous examples used to help fund corporate efforts to adopt green technologies.

“We will further expand such initiatives and work toward realizing a stronger economy,” he said.

Bridging bonds are designed to cover temporary funding shortfalls on the premise that future funding resources can be secured. The Finance Ministry classifies them differently from deficit-covering bonds, and other recent examples have included special bonds issued to fund childcare programs.

The proposal comes as concerns over Japan’s fiscal outlook continue to simmer in the bond market. Japan’s 10-year government bond yield briefly climbed earlier this month to the highest level since 1996 amid worries over the Takaichi administration’s pro-spending fiscal stance. The bridging bond plan appears aimed at avoiding further alarm over large-scale issuance of deficit financing bonds, though market concerns over the repayment plan could weigh on bonds.

The idea was originally proposed by the Liberal Democratic Party’s Growth Strategy Headquarters. In a proposal released Thursday, the group called for the creation of a new investment framework dedicated to growth and crisis management spending. The paper said such funding should be managed separately from ordinary fiscal spending through the use of bridging bonds.

The market remains unconvinced. “At the end of the day they are still government debt,” Keisuke Tsuruta, a senior fixed-income strategist at Mitsubishi UFJ Morgan Stanley Securities, said in a report Thursday.

“If the government increasingly relies on such bonds to expand spending before securing stable funding sources, markets may view that negatively from the perspective of fiscal discipline,” he said.

Kihara sought to assure investors that the government would continue to take a responsible approach to fiscal policy, saying, “the government would ensure fiscal sustainability by steadily lowering the debt-to-GDP ratio, while maintaining firm market confidence.”