LONDON — Britain's takeover regulator has given BHP Billiton until Feb. 6 to either formalize its multibillion-dollar takeover proposal for mining giant Rio Tinto or say it is not interested.

The move comes after Rio Tinto, which owns Kennecott Utah Copper, invoked Britain's so-called "put up or shut up" laws, which stipulate that a company subject to a potential bid can request that a time limit be imposed on would-be buyers to clarify their intentions.

Rio Tinto PLC, which is based in London but is also listed in Australia, has already rejected a proposed BHP Billiton Ltd. offer — valued at around $130 billion — explaining that it was massively undervalued.

The British deadline now forces BHP to come up with a formal offer or drop its bid altogether.