The U.K. Takeover Panel Friday ruled that Anglo-Swiss mining company Xstrata PLC (XTA.LN) must "put up or shut up", and formalize its offer for rival Anglo American PLC (AAL.LN) by Oct. 20, or walk away from the deal.

If it doesn't make an offer, Xstrata will not be able to approach Anglo-American again for six months.

Market watchers reckoned Xstrata won't make an imminent move on Anglo, saying it has enough on its plate already.

Xstrata first proposed a merger with Anglo American in June, to create a company with a market capitalization of around $80 billion, but Anglo-American rejected the plan. It reiterated its rejection Friday, saying Xstrata's proposal is not in the interest of its shareholders.

Analyst Charles Kernot of Evolution Securities said Xstrata is unlikely to make a fresh move for Anglo by the end of the month.

"One reason Xstrata accepted this is that they have other problems to deal with," he added, saying the company is already tied up with its 25% shareholding in peer Lonmin PLC (LMI.N). Kernot said Xstrata, which he rates reduce with a target price of 820 pence, could come back in six months with another offer, but reckons it's "unlikely".

Xstrata last year raised its stake in platinum producer Lonmin to 25%, after walking away from a GBP5 billion hostile offer for that company due to tough debt markets.

It's now free to renew its takeover bid for Lonmin, but isn't expected to do so, analysts said. Liberum Capital said Xstrata is more likely to revisit its Lonmin options in the second quarter of next year, after the Anglo proposal has played out. Xstrata has declined to comment on the matter.

Takeovers among miners have picked up pace as companies struggle to survive as independent entities. A combined Xstrata-Anglo could generate cost savings of up to $1 billion a year, increase its exposure to a greater mix of commodities and be more competitive relative to larger peers including BHP Billiton (BHP.AU).

At 0725 GMT, Xstrata shares were down 2.5% or 21 pence to 851p, while Anglo-American was down 0.7% or 14p to 1872 pence.

Web site: www.thetakeoverpanel.org.uk

-By Elizabeth Adams, Dow Jones Newswires; +44 (0) 20 7842 9386; elizabeth.adams@dowjones.com (Jeffrey Sparshott in London contributed to this article.)