By Christopher Johnson

London - Brent crude oil slipped to around $114 a barrel on Wednesday on worries over economic growth and ahead of a European Central Bank (ECB) meeting expected to announce new measures to tackle the region's debt crisis.

ECB President Mario Draghi is expected to back up his pledge to do “whatever it takes” to save the euro when he presents details on Thursday of a new bond-buying plan designed to ease the deepening euro zone crisis.

Investors also awaited US jobs data on Friday for clues on the health of the world's biggest economy. A soft jobs report could strengthen the case for a third round of monetary easing (QE3) from the Federal Reserve when it next meets in September.

Since late 2008, the Federal Reserve has bought $2.3 trillion in long-term securities in a drive to spur growth, indirectly pumping billions into assets markets and injecting huge liquidity into oil and commodities and boosting prices.

Brent crude futures for October fell 20 cents to $113.98 a barrel by 0845 GMT. US crude futures slid 40 cents to $94.90.

“The market hopes the ECB will do something special to solve the euro zone's problems,” said Carsten Fritsch, oil analyst at Commerzbank in Frankfurt.

Worries about economic growth moved centre stage after data showed that US manufacturing shrank at its sharpest clip in more than three years in August, while separate releases showed exports and hiring in the sector also slumped.

The next big test for the US economy will be the August unemployment data. The median forecast in a Reuters poll is for a gain of 120,000 jobs, down from 163,000 in July.

The data is crucial as Federal Reserve Chairman Ben Bernanke in a speech at a Fed symposium last week said the weak job market and 8.3 percent unemployment was a “grave concern”.

Investors were paring expectations from the ECB's Thursday meeting, after driving markets higher on hopes it will detail a bond-buying plan to help out its crisis-ridden members.

Germany's Constitutional Court will rule on September 12 whether the euro zone's bailout fund is compatible with German law, and the ECB may not be able to do anything significant until then.

Hopes for ECB bond buying had been raised on Monday after Draghi said that short-term sovereign bond purchases would not breach European Union rules.

Prices were supported by the dispute between Iran and Israel after the leader of Lebanese Iranian-backed militant group Hezbollah said Tehran could hit US bases in the Middle East in response to any Israeli strike on its nuclear facilities.

Concerns that sanctions on Iran's crude shipments would hurt global supplies have abated, as some of its biggest buyers are finding ways to continue buying crude from Tehran.

Sanctions on Iran have led to a debate on the release of strategic petroleum reserves to rein in prices and enhance their effectiveness. The head of International Energy Agency (IEA) said on Tuesday that crude markets are well-supplied.

The markets will also be awaiting weekly US oil inventory data due from the American Petroleum Institute (API) on Wednesday and from the Energy Information Agency (EIA) on Thursday, a day later than usual because of a US holiday this week.

A survey of six analysts forecast that crude stocks would drop 5.3 million barrels on average for the week ended August 31. - Reuters