The unprecedented $9 trillion rescue mission by central banks to haul the world economy from its coronavirus recession is being tested as rising bond yields and inflation bets threaten their ability to keep borrowing costs down.

While Federal Reserve Chairman Jerome Powell this week called the recent run-up in bond yields “a statement of confidence” in the economic outlook, other counterparts are sounding less sanguine as their recoveries lag that of the U.S..

European Central Bank President Christine Lagarde said Monday that she and colleagues are “closely monitoring” government debt yields. The Bank of Korea warned it’ll intervene in the market if borrowing costs jump, Australia’s central bank has been forced to resume buying bonds to enforce its yield target and the Reserve Bank of New Zealand Wednesday promised a prolonged period of stimulus even as the economic outlook there brightens.

The bond market isn’t listening, tumbling again on Wednesday. U.S. 30-year Treasury yields surged as much as 11 basis points to 2.29%, their highest level since before the coronavirus-induced meltdown in March. The rate on similar-dated U.K. bonds also soared, with Germany’s following suit.

Because government borrowing costs are used as the benchmark for pricing loans to businesses and consumers, any increase in yields trickles through to the real economy. That counters the campaign by central banks to drive recoveries with cheap money, potentially forcing them to deliver even more stimulus at some point.