The Bank of Japan’s extraordinary bond market intervention this week has magnified the spotlight on its quarterly asset purchase plan due Thursday.

The central bank’s resolve to cap the rise in 10-year yields — seen in unlimited purchase operations Monday and Tuesday — has increased investor focus on its plans for longer-dated maturities. They lie outside the BOJ’s yield-curve control policy and remain particularly vulnerable to volatility in the global bond market.

The 30-year yield broke through the 1% level Monday for the first time in six years and traded at 1.1% on Tuesday — steepening Japan’s yield curve. Benchmark yields held within policymakers’ limits as investors sold ¥242.6 billion ($2 billion) of the bonds to the central bank.

It’s unlikely the BOJ will keep purchases unchanged, "with an increase in 5 to 10 years almost certain, and even a slight boost to superlong bonds won’t come as a total surprise,” said Takafumi Yamawaki, head of local rates and currencies research at JPMorgan Securities Japan Co. in Tokyo. "The rise in overseas yields exerts upward pressure on superlong JGB yields and the recent steepening appears to be detrimental for the BOJ’s policy of defending the 10-year cap.”

The BOJ intervened in an unprecedented manner Monday after a global bond rout pushed benchmark yields to the upper end of its 0.25% line in the sand. Officials remain committed to keeping policy loose, to boost Japan’s moribund economy, even as surging inflation worldwide spurs peers such as the Federal Reserve to roll back stimulus and raise interest rates.

The central bank conducted two unlimited purchase operations Monday and announced plans for more through Thursday, a move that sent the yen plummeting to a seven-year low. It is the first time it has intervened over such a sustained period.

The BOJ is scheduled to release its regular bond buying plan for April to June on Thursday. It last made tweaks to purchases in July, when it moved from a monthly to a quarterly schedule, and has kept amounts and frequencies unchanged since then.

The current plan includes monthly purchases of ¥425 billion of 5 to 10 year bonds and ¥50 billion of those with a maturity over 25 years.

Still, rather than altering its fixed schedule, the BOJ could use so-called irregular operations to boost purchases at any time in order to cap a rise in superlong yields. It last used such a measure in March 2020, for 10 to 25 year maturity bonds.

It has never used unlimited fixed-rate options for longer-dated bonds having expressed concerns that if their yields were too low, that would hurt investors and the economy.

"The BOJ probably doesn’t want to tweak the scheduled plan as it would become challenging to reduce purchases later,” said Katsutoshi Inadome, a strategist at Mitsubishi UFJ Morgan Stanley Securities in Tokyo. "While keeping quarterly amounts steady, it may use unscheduled operations or unlimited fixed-rate buying to respond to rising superlong yields.”