Swiss commodity trader Glencore International will close the books for its planned $11 billion initial public offering on May 17, a day ahead of schedule, underscoring strong demand for the offer despite the recent downturn in commodity markets.

No reason was given for the early close in a term sheet seen by Thomson Reuters IFR on Friday. Sources previously told Reuters that order books were fully covered on the first day after strong interest from investors.

'This is a good sign,' said Alex Wong, a director with Ample Finance Group. 'But the retail demand for the offer is unlikely to be strong because of the recent slump in commodity prices,' he said.

Glencore officials were not immediately available for comment. Usually a decision to close books early is a sign of strong demand for the offer.

On Thursday, Glencore chief executive Ivan Glasenberg told a media conference that the IPO had generated strong demand.

Commodity price volatility since last week has prompted market worries over Glencore's planned IPO, set to be London's largest ever, with fund managers last week sensing an opportunity to drive down the price.

An early close will also give the underwriters more time to orderly allocate shares to investors spread across the globe.

'Books will close one day earlier than previously announced. The only exceptions to be made are for investors with meetings thereafter,' the term sheet said on Friday.

'We haven't seen much pullback with the recent drop in commodities prices,' Glasenberg said while announcing the Hong Kong retail offer, which opened on Friday. He blamed the volatility in commodities prices on speculators.

The Hong Kong offer aims to capitalise on the deep pockets of investors in the region, who are well acquainted with surging demand for metals and other natural resources from fast-growing economies in China and India.

No other terms of Glencore's offer were changed, the sheet showed. Glencore launched the much-anticipated global IPO, with a dual listing in London and Hong Kong, last week and set a price range of 480-580 pence per share.

Under the original terms, Glencore was due to announce the final pricing on May 19.

The listing will boost Glencore's firepower for deals but will also push it into the public eye after 37 years as a discreet private company.

A successful listing will be a big fee event for 23 banks who are working with Glencore on the deal. The banks can share up to $275 million in fees if the full target of $11 billion is raised.

Citigroup , Credit Suisse and Morgan Stanley are the joint global co-ordinators for the offer, joined by another 20 banks in lower ranking syndicate roles.-Reuters