The two shareholders together own 3.6% of Xstrata said the deal undervalued their shares.
Xstrata has formally announced plans to merge with Glencore to create a $90bn combined group to be named Glencore Xstrata International.
Xstrata Chief Executive Mick Davis said the two companies would have to work hard to bring some of his shareholders on board.
It requires only 16.5% of shareholders to vote down the deal, code-named Project Everest.
"We clearly have to now go to our shareholders and speak to them and take them through the transaction … we’ve got a long gestation period, we recognise that," said Davis.
Merger ratio of 2.8 New Glencore shares for every Xstrata share held, which providing Xstrata shareholders other than Glencore with a 45% stake in the combined entity.
The deal which is a merger of equals will create a group along the commodities value chain, from mining and processing, storage, freight and logistics, to marketing and sales.
Xstrata CEO Mick Davis will be appointed as CEO of the combined group while Ivan Glasenberg, current Glencore CEO, will be the Deputy CEO and president of the new company.
