Three of the world's most powerful central banks hold key meetings next week, and their decisions will either weigh on a global economy slowing so much the International Monetary Fund recently cut its growth forecast or give it a desperately needed shot in the arm.

The Federal Reserve, July 31-Aug. 1, European Central Bank, Aug. 2, and the Bank of England, Aug. 2, are all set to meet within 24 hours. The IMF recently cut its 2013 global economic growth forecast to 3.9 percent from 4.1 percent, owing to euro zone concerns.

Analysts give 50-50 odds the Federal Reserve will opt for a third round of quantitative easing after calls from influential leaders such as Dennis Lockhart, president of the Federal Reserve Bank of Atlanta, to consider further attempts to resuscitate an economy that has an 8.2 percent jobless rate and an output gap as large as 5.5 percent, according to the Congressional Budget Office.

Quantitative easing commonly refers to central banks increasing their balance sheets to increase the credit available for lending.

Fed Chairman Ben Bernanke recently testified to Congress that the Federal Reserve was considering multiple new stimulus plans, including pushing short-term interest rates lower and buying mortgage-backed or Treasury securities. But he refused to give a specific time frame for any additional stimulus, which has led experts to believe the Federal Reserve won't announce further policy stimulus, when it meets on July 31 and Aug. 1.

"As it stands at the moment, the incoming news has probably not been quite weak enough to prompt the Fed into providing more policy stimulus, such as a third round of asset purchases (QE3), at the meeting that concludes next Wednesday," Capital Economics said in a July 25 statement.

Even without QE3, the Federal Reserve could launch a funding-for-lending scheme similar to the one the Bank of England uses. Bank of America, in a July 26 note, said it expects the Federal Reserve to announce a $600 billion quantitative easing program on Sept. 13.

European Central Bank

European Central Bank President Mario Draghi said Thursday that policy-makers will do whatever is necessary to preserve the euro, strongly implying a commitment to buy bonds from debt-choked nations like Spain and Italy. 

"His comments certainly suggest that ECB purchases of Spanish and Italian bonds are back on the table for discussion," Chris Scicluna, head of economic research at Daiwa Capital Markets Europe, told Bloomberg News about Draghi's most recent comments.

The ECB had been willing to buy bonds from strained markets as recently as four months ago, but ended the operation in order to force individual governments to do more on their own, according to Ken Wattret, chief market economist for the euro region at BNP Paribas SA.

If the markets perceive that the ECB is resuming bond-buying, it should boost risk assets like stocks and commodities.

Investors also will be watching for signals that ECB is willing to give Europe's bailout fund, the European Stability Mechanism, a banking license. Giving the ESM a banking license would "significantly boost its firepower," according to Capital Economics, but Draghi is expected to resist the pressure to provide it one. The license would allow for the ESM to borrow from the ECB to prevent countries from financially collapsing.

"The ECB wants to see government money used first," Marco Valli, an economist at UniCredit Global Research, told Bloomberg News.

Other areas to watch include whether the ECB will follow up July's interest rate cut with further cuts or bring back its securities markets program after being out of service for the last six months. The ECB is not expected to endorse a quantitative easing despite recent calls from the International Monetary Fund.

Whether any of these measures will be effective is in doubt, according to Roberto Perli, managing director at International Strategy & Investment Group Inc., because "the lending channel is broken."

Bank of England

The Bank of England is expected to further cut already low interest rates and undertake more asset purchases. It will attempt to do enough to prevent the United Kingdom losing its AAA credit rating, which a Reuters poll calculated as a one-in-three chance. It would be "unlikely for it to lose its safe-haven status" if its credit rating was downgraded, according to Capital Economics, but it still represents a very real threat.

Capital Economics expects the Bank of England to cut its benchmark rating from 0.5 percent, a record low, down to 0.25 percent, though the cut is expected to boost GDP by just 0.1 percent. Finding a way to boost GDP any way it can has become a massive priority for the Bank of England after a devastating GDP report on Wednesday. The UK economy shrank the most since 2009, with GDP falling 0.7 percent -- a massive decline compared to 0.2 percent decline estimates.

In response to the GDP decline, the IMF said "further monetary stimulus is required" and that the United Kingdom should scale back its scheduled fiscal tightening.

JPMorgan Chase & Co. predicts a boost in quantitative easting from its current level of £375 billion. Reuters estimated that it should increase the level to £400 billion by November.

The central bank had hoped quantitative easing could be held off through its funding-for-lending program, which rewards banks that lend with cheaper financing. The program allows banks to borrow treasury bills and collateral and have as many as four years to repay the loans, which as Bloomberg notes, could leave the Bank of England "exposed to potential balance sheet losses."