The Federal Reserve, in a surprise announcement, set in motion a plan Friday to ease unexpected strains seen in short-term money markets last month.

The Fed said it will start to expand its balance sheet next week by purchasing U.S. Treasury bills, adding reserves to the financial system to avoid a recurrence of the unexpected strains seen in short term money markets last month.

At the same time, the Fed will extend its schedule of overnight and more longer-term repurchasing agreement operations to ensure that the supply of reserves remains ample and to mitigate the risk of money market pressures.

Last month, the Fed was forced to step into contain stressing in funding markets after the overnight repo rate, or how much banks and hedge funds have to pay for short-term borrowing, rose so high that the Fed’s benchmark interest rate pushed above its target range.

The Fed disclosed that its interest-rate setting FOMC committee had an unscheduled meeting on Oct. 4 to discuss the situation in the short-term lending markets.

The FOMC voted unanimously to begin to purchase Treasury bills at an initial pace of about $60 billion per month starting Tuesday. The purchases will last at least into the second quarter of next year.

The Fed said the T-bill purchases will keep the level of reserve balances held at the Fed “at or above the level that prevailed in early September.”

The Fed statement said that the actions “are purely technical measures” and “do not represent a change in the stance of monetary policy.”

Some economists have argued that the purchases are a soft form of quantitative easing, known as QE, that was put in place in the wake of the 2008 financial crisis. During the crisis, the Fed bought trillions of dollars in assets in an effort to push down long-term bond rates.

By limiting the purchases to T-bills, the Fed hopes to avoid any comparison to the crisis-era QE.

“Purchases of Treasury bills likely will have little if any impact on the level of longer-term interest rates and broader financial conditions. As a result, these purchases should not have any meaningful effects on household and business spending decisions and the overall level of economic activity,” the Fed statement said.

Read: Powell says planned bond buying isn’t emergency stimulus; investors are skeptical

Under the details of the plan, longer-term repo operations will be conducted twice per week, initially in an offering amount of at least $35 billion. Overnight repo operations will be conducted daily, in an offering amount of at least $75 billion per operations.