The euro gained on Friday on hopes that the European Central Bank may get involved in a plan to help struggling euro zone countries, but world stocks fell as many investors continued to fear a spread of the region's debt crisis into core European economies.

Wall Street indexes ended mixed, capping the worst week for U.S. stocks in two months.

U.S. Treasury prices fell as the borrowing costs of troubled European countries declined slightly, reducing the appeal of safe-haven assets. Yields on Spain's bonds eased modestly before weekend elections.

Reports that the ECB is considering lending to the International Monetary Fund to bail out troubled euro zone economies shored up investor sentiment.

Speculation that the ECB could step up purchases of European sovereign debt also helped.

Either approach would be satisfactory, said Andrew Busch, senior currency strategist at BMO Capital Markets in Chicago. The broader point is that the ECB is finding a way to stabilise the European debt crisis, he said.

Economists say only the ECB would have enough fire power to quell a confidence crisis spreading throughout the euro zone. But EU law forbids the bank to finance government borrowing directly, thus the possible arrangement with the IMF.

This third-party lending arrangement not only works around ECB laws, but also provides an avenue for the ECB to create enough funding to stabilise the crisis while maintaining its appearance of independence, Busch added.

The euro zone common currency rose 0.4 percent to $1.3509, pulling away from a five-week low of $1.3420 struck on Thursday.

Apparent disagreement between Germany and the UK about how to solve the European debt crisis kept investors on the edge, however.

At a news conference in Berlin, the leaders of both countries sent out conflicting messages to markets, with British Prime Minister David Cameron calling for decisive action to stabilise the euro zone and German Chancellor Angela Merkel favouring a step-by-step approach.

On Wall Street, the Dow finished higher but the Nasdaq slid. The S&P 500 finished nearly flat, holding above a key resistance level around 1,200, but still down 3.8 percent for the week.

The Dow Jones industrial average edged up 25.43 points, or 0.22 percent, at 11,796.16. The Standard & Poor's 500 Index dipped 0.48 point, or 0.04 percent, to 1,215.65. The Nasdaq Composite Index was down 15.49 points, or 0.60 percent, at 2,572.50.

In Europe, the FTSEurofirst 300 finished 0.7 percent lower. World stocks, measured by the MSCI All-Country World Index, declined 0.6 percent.

The (market's) scepticism comes from the realization that there is no magic bullet in place to solve this crisis, said Giancarlo Perasso, chief economist at Redux-Matrix.

U.S. crude oil prices settled $1.26 down at $97.67.

Benchmark 10-year U.S. Treasury notes fell 13/32, sending their yield up to 2.01 percent, as a decline in Italian government bond yields reduced their safe-haven bid.

Yields on Italian 10-year bonds eased to 6.7 percent but stayed near levels investors consider unsustainable.

Spanish 10-year bond yields fell to 6.4 percent from Thursday's 6.5 percent before weekend elections in which the centre-right People's Party is expected to win a resounding mandate to slash public spending.

(Additional reporting by Wanfeng Zhou in New York; Editing by James Dalgleish and Dan Grebler)