A committee of Wall Street advisers is pouring cold water on a proposal by U.S. Treasury Secretary Steven Mnuchin to issue superlong 50-year and 100-year U.S. government bonds, arguing that the big pension funds and insurers expected to buy the securities won’t have much interest.

The Treasury’s Borrowing Advisory Committee, composed of representatives from some of the largest financial institutions that participate heavily in the bond market, told the Treasury that “the committee does not see evidence of strong or sustainable demand for maturities beyond 30 years.”

The committee meets quarterly, in advance of a regular release by the Treasury on its plans for financing the U.S. debt. Currently, the U.S. Treasury issues no debt longer than 30 years. Mnuchin has argued that ultralong bonds could be a useful tool for locking in today’s low borrowing costs for a very long time. Last month, the Treasury requested the advisory committee analyze the viability of bonds longer than 30 years.

Monique Rollins, the acting assistant secretary for financial markets, said that despite the advisory committee’s cool response, the Treasury would “continue to study” longer-term bonds and seek input from a “broad community” beyond just those on the committee. An update will be provided at a future quarterly announcement, the Treasury said.

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