Commodities major Glencore could, under UK rules, return with a buyout offer for global miner Rio Tinto April onward.

Investors believe the main hurdle to a deal will be whether Glencore, which is 8.4% owned by billionaire Ivan Glasenberg, will table a large enough premium.

However, they have played down the chances of Glencore making a fresh bid in the near future given that the Anglo-Swiss firm's stock has fared poorly as against Rio's since October 2014.

Shares in Glencore have lost some 9.66% over the past three months in London trade.

By comparison, shares in Rio have gained 7.31% during the same period in London.

Glencore's market value has fallen some 11% to £39.19bn (€54.5bn, $61.9bn) since its 2014 bid was revealed, while the Anglo-Australian firm's market cap has climbed some 6% to £59.22bn.

Ric Ronge, a portfolio manager at Pengana Capital, told Reuters: "Given Glasenberg's reputation and large personal stake in Glencore, the company is unlikely to offer meaningfully over what the market believes, rightly or wrongly, Rio is worth.

"But I think it is foolish to underestimate Glencore, given the success of the company to date."

Media infatuation

Earlier, Rio Tinto chief executive Sam Walsh said his firm will not be bought over by Glencore because there was no value in it for shareholders and because regulators will never let it happen.

Speaking at the Royal Institute for International Affairs in London on 22 February, Walsh said that while "the media are sort of infatuated with this", investors did not expect a deal.

When asked about consolidation among the world's biggest miners, Walsh said: "Investors say: 'I don't get it. Why are you giving this any air, because it actually isn't going to happen.'"

"Now, part of the reason is value. Part of the reason is, as you say, the antitrust and people who collect tax and what have you, they're just simply not going to let it happen."

Rio revealed last October that it had rejected a takeover approach from Glencore, made in August, to create a $160bn mining and trading behemoth.

Walsh has said a merger of the firms will not work because of a clash of cultures: Rio is a mining firm focused on developing low-cost, long-life mines, while Glencore is a trading firm operating on a short-term horizon.

Value and regulatory opposition were the chief reasons behind BHP Billiton's failed takeover offer for Rio Tinto in 2008.