By planning to raise interest rates during a chorus of objections, Jean-Claude Trichet is embarking on his biggest gamble since assuming the presidency of the European Central Bank more than two years ago.

The economic recovery of the 12-nation euro zone is just picking up steam, but patchy economic reports continue and inflation is starting to cool. That is helping fuel opposition to the ECB as finance ministers, international think tanks and unions argue that low rates still are needed for the nascent recovery.

Nevertheless, Trichet strayed from a speech 13 days ago to read from a specially prepared note. His unexpected message: The ECB would raise rates to curb incipient inflation. The move is widely expected to come today and would be the first time the ECB has raised rates in five years.

Trichet, on the defensive ever since delivering his recent message, argues that keeping inflation low is the best way to promote growth and create jobs. The ECB chief fears for the bank's credibility after the bank overshot its inflation target for six of the past seven years.

At stake is the reputation of Trichet and the ECB. The health of the euro-zone economy, similar in size to that of the United States, also hinges on the outcome. As a major global trading partner, Europe's well-being is crucial for the world economy.

"The risk of a monetary-policy mistake by the ECB has never been higher," says Jean-Michel Six, chief European economist of Standard & Poor's Ratings Services in London. "They could raise rates too early and nip recovery in the bud, or too late and we could see significant inflation."

Signs of inflation are beginning to emerge around the globe. The cause is largely higher energy prices. The price of oil is up some 50 percent this year. Central banks around the world have already begun increasing rates to tame inflation, with the U.S. Federal Reserve already raising rates at 12 consecutive meetings.

Europeans are sensitive to higher rates now because growth is far lower and more uncertain than in the United States, and unemployment is far higher at 8.4 percent, compared with around 5 percent in the United States.

Overall sentiment for the euro zone slipped in November for the first time in five months, figures from the European Commission showed yesterday, raising speculation that a recovery once again will falter.

On top of that, annual inflation slowed for a second consecutive month to 2.4 percent in November, figures also showed yesterday, down from a peak of 2.6 percent in September and closer to the ECB's goal of just under 2 percent.

Many disagree with Trichet. "We see the planned increase . . . as a burden to the fragile revival," said a spokeswoman for IG Metall, one of Europe's largest unions. Labor leaders are frustrated that low wage increases of past years haven't yielded more jobs.

Jean-Claude Juncker, the president of the euro-zone finance ministers, said this week that a rate increase could prompt unions to demand higher salaries, triggering the "second-round effects" that the ECB is trying so hard to avoid. And the Paris-based Organization for Economic Cooperation and Development this week urged the ECB to wait until late next year to raise rates.

Though the economic outlook hasn't changed much, the threat to inflation has, in the ECB's eyes. Loan growth has been soaring, prompting fears the bank's low rates might be fueling unsustainable rises in housing prices. Figures this week showed loans for home purchases soared an annual 10.8 percent in October from 10.5 percent in September.

In office since November 2003, Trichet has always pledged he wouldn't move rates out of the blue. But last week, he confused markets when he told the European Parliament that the bank wasn't planning on a series of rate increases. An isolated move by a central bank is rare and often meaningless in controlling inflation or steering growth.

An assurance there won't be a series of increases "takes away the effect" for markets, says Thomas Mayer, chief European economist at Deutsche Bank in London.