Glencore Chairman Simon Murray gave no details, telling shareholders in Zug, Switzerland, only that there had been "developments", hinting at an improved deal.

"It has happened very recently, overnight," he said.

Glencore's bid had been teetering on the brink of collapse after Xstrata's second-largest shareholder, Qatar, said it would vote against Glencore's offer of 2.8 new shares for every Xstrata share held.

"If Glencore's adjourning the meeting then it looks like they probably will be raising the exchange ratio," said an analyst who declined to be named.

Xstrata shares were up 6 percent at 1,037.5 pence at 0840 GMT, while Glencore's were down 1.44 percent at 386.7p, indicating that the market thinks so, too.

One of Xstrata's largest 40 shareholders expressed surprise at the last-minute adjournment and was hopeful of a bump-up in terms.

"The deal as was wasn't going to happen, so maybe (Glencore Chief Executive Ivan Glasenberg) has come in with an eleventh-hour revision. Compromise of exchange ratio of 3?"

Glencore said in a statement it was "considering its options" and would update the market in due course. In the meantime it has asked for its shares to be suspended in London and Hong Kong.

Glencore investors were due to have met at 9 a.m. (0700 GMT), with Xstrata's shareholders meeting two hours later, also in Zug, Xstrata's home base.

"In situations like this, as you can imagine, people are working to reach a deal as quickly as possible," said a source familiar with the process.

Other sources familiar with the process said it was not clear a deal could be hammered out in time before the Xstrata shareholder meeting.

"The whole thing is on ice," said another.

If Glencore has changed the terms of its offer at the last minute, both companies would have to delay the shareholder votes to meet regulatory requirements, probably by at least two weeks.

Under the deal's structure, holders of just 16.5 percent of Xstrata shares needed to vote against the tie-up for the deal to collapse, and Qatar, with 12 percent, said last week it would vote against the Glencore proposal, making it very unlikely the bid would go through without an improvement, or some accommodation between the two.

Qatar and Glencore had not met since the Gulf state's sovereign wealth fund demanded an improvement in June to the trader's offer, and both sides had said they would stick to their positions.

Glencore, with a 34-percent stake, has long coveted a full tie-up with Xstrata to create a mining and trading powerhouse. It made its move in February, less than a year after listing its own shares, which in turn had been largely motivated by the desire to do more ambitious deals.

Qatar and Xstrata spokespeople declined to comment.

($1 = 0.6275 British pounds)

(Additional reporting by Sinead Cruise, Sarah Young and Dinesh Nair; Editing by Will Waterman)

• A Permanent Economic Emergency