Q&A: What is tapering?
Since late 2012, the US central bank, the Federal Reserve (or simply the Fed), has been spending $85bn a month to boost the US economy.
That is the most recent phase of quantitative easing (QE), a policy that began as response to the financial crisis that struck in 2007.
Under the plan, the Fed has been buying assets, mainly US government debt, which has the effect of driving down US interest rates, including the cost of mortgages, car loans and financing for business.
But the Fed is expected to reduce that spending in a process dubbed tapering.
The Fed may judge that the economy has become robust enough to recover without as much support.
There has been a slow recovery since the economy emerged from recession in June 2009.
Economic growth picked up to an annual pace of 2.5% in the second quarter - not spectacular, but a steady improvement.
Unemployment has fallen to 7.3%, not far from the target of 7% set by the Fed, although critics argue that this number has been flattered by people leaving the labour force.
The Fed may also want to get started now, as October could bring a political battle in the US over the government's debt ceiling and the Fed may not want to make a significant policy change while that fight is going on.
What will the Fed do?
As the word taper suggests, the Fed is likely to phase out its support for the economy slowly.
Economists think the purchase of assets might be cut by about $10bn a month.
The chairman of the Fed, Ben Bernanke, may also soften the blow by pledging to make no further cuts over the next few months.
There will also be interest in what sort of assets the Fed chooses to buy in the future.
At the moment, it mainly buys government debt and mortgage debt.
Some economists think it may continue to buy mortgage debt at the current rate, because it has a direct impact on the property market.
Others think the Fed may cut back on that, because it is becoming too large a presence in the mortgage market.
So how much has the Fed committed?
The accounts of the US Federal Reserve show that its balance sheet has expanded from about $1 trillion before the crisis hit in 2007 to almost $3.8tn, and that is likely to expand further.
The majority of that expansion is due to the purchases made under QE.
It is hard to conceive of numbers that big.
Perhaps this might help: the combined value of the three biggest US technology companies - Apple, Google and Microsoft - is a little over $1tn and the total value of the UK economy in 2013 was $2.4tn.
That is a lot of money. Did it work?
The Fed bought debt, mainly US government bonds and mortgage-backed debt.
That drove down borrowing costs across the economy. By late 2012, mortgage rates fell to record lows, which contributed to a recovery in the housing market.
Other areas of the economy that are sensitive to interest rates, including car sales, have also picked up.
It was also hoped that investors would switch money away from the poor returns of government debt into shares and corporate debt - and the stock market has seen a strong run.
The US Federal Reserve itself said in March that the asset purchase programme had had a "meaningful" effect in easing financial conditions.
It estimates that the policy has boosted employment in the private sector by two million.
Were there any unintended consequences?
The Fed's main goal was to keep interest rates low in the US and boost economic activity at home.
But the policy encouraged investors to look overseas for assets which promised a better rate of return than US government debt.
Some of those funds are now returning home. In fact, recent volatility on emerging markets is being blamed on the threat of tapering.
Last month, the head of the International Monetary Fund, Christine Lagarde, warned that central banks should be careful when withdrawing stimulus, highlighting the recent volatility on emerging markets.