(Bloomberg) -- The U.S. Treasury’s plan to restart issuance of 20-year bonds will mean only marginal cuts, if any, to other coupon-bearing auctions, Wall Street dealers say.

How Treasury rejiggers its lineup depends on when 20-year sales begin and their size, analysts say. Most are eyeing the May refunding as the likeliest timing, rather than next month’s. Waiting closer to mid-year is seen as reducing the need to shave auction sizes, which have swelled to historically large sizes, leaving Treasury well-funded for now.

But the federal deficit is set to surpass $1 trillion, and the Treasury also has to deal with a wall of debt starting to mature later this year. As a result, any move to shrink offerings of other coupon-bearing maturities to make room for the 20-year would soon have to be reversed. And if the Treasury does take that step, bills are seen as the most likely candidate.

“The key reason for Treasury to introduce the 20-year now is that it gives it a warm-up period,” said Jim Vogel, a strategist at FHN Financial. “It will be absolutely necessary later on for larger auction sizes overall,” so cuts now would only be temporary.

Traders reacted to the prospect of more long-term debt by driving the yield curve steeper across maturities. The extra yield on 30-year bonds over 2-year notes rose about 3 basis points, the most this month, to 0.72 percentage point.

For decades, the Treasury has sought a regular and predictable approach to issuance, which it sees as fostering investor demand and reducing the cost to taxpayers. That approach has meant that officials prefer not to make abrupt or frequent changes to their auction slate.

The decision to reboot the 20-year, which the U.S. stopped issuing in 1986, appears to put on ice for now the prospect of even longer maturities. Treasury Secretary Steven Mnuchin has been pondering that step since he took over in 2017. The 20-year idea seemed to gain traction last quarter.

There’s another key reason analysts say the Treasury can wait a few months to introduce the two-decade maturity. Its financing position is getting a boost from the Federal Reserve’s monthly purchases of $60 billion in T-bills, a program aimed at increasing reserves. As those securities mature and the central bank rolls them over, it reduces the amount the government needs to borrow from the public.

“Based on the current auction sizes and projections for the deficit, it seems unlikely to us that Treasury will start issuing the 20-years in February, but they will likely announce in May the actual start of sales,” said Zachary Griffiths, a rates strategist Wells Fargo Securities. “And at that time, Treasury could start 20-years a bit smaller than its full annual run-rate plans, or if not, just cut the 30-year auctions by a few billion.”

It will likely leave the 10-year alone, because its role as the world’s borrowing benchmark means it needs to be highly liquid, according to Griffiths.

Well Fargo forecasts that when the 20-year is fully up and running, Treasury will sell about $39 billion quarterly, or about $150 billion to $160 billion each year. The Treasury Borrowing Advisory Committee has recommended that the government issue $140 billion annually.

More information on the 20-year will come at Treasury’s next quarterly announcement of longer-dated debt sales, on Feb. 5, the department said in a statement. In its regular quarterly survey released Friday, Treasury asked dealers about the maturity, including their view on the minimum auction size and total issue size necessary to ensure benchmark liquidity.

“Treasury will likely do this in a way to limit adjustments needed in other coupon maturity sizes, or even prevent any from occurring at all,” said Mark Cabana, head of U.S. interest rates strategy at Bank of America Corp.

--With assistance from Saleha Mohsin.

To contact the reporter on this story: Liz Capo McCormick in New York at emccormick7@bloomberg.net

To contact the editors responsible for this story: Benjamin Purvis at bpurvis@bloomberg.net, Mark Tannenbaum, Nick Baker

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