Some $40-billion in value could be wiped from Rio Tinto's market value if it abandoned BHP Billiton's proposed merger bid, UK newspaper Sunday Times reported at the weekend.
Rio Tinto's share price has been the biggest riser in the FTSE 100 this year, but the company has resolved to keep BHP Billiton at arm's length.
The world's third-largest mining group has thus far thwarted BHP Billiton's attempts to discuss its three-for-one share offer to create a $400-billion resources super-major.
Valued at $153-billion, the proposal has been dismissed by Rio Tinto as undervaluing the company and prospects.
In the meanwhile, the Sunday Times reported that BHP Billiton might submit an unchanged bid for Rio Tinto after it was forced into a corner by the takeover target.
Rio Tinto approached the UK takeover's panel earlier this month to exercise the UK competition law's "put up or shut up" clause, which resulted in BHP Billiton being issued with a deadline of 6 February to either make an offer or back off.
Most analysts have suggested that BHP Billiton could raise its current informal offer to a ratio closer to four shares for every Rio Tinto share, but the Sunday Times suggested that BHP Billiton boss Marius Kloppers and his advisers may "want to test the resolve of Rio's investors" by submitting an unchanged formal bid.
"This is one of several options being considered along with increasing the cash component of any bid. But BHP has not made a decision and it is expected to wait some weeks before it does," the newspaper reported.
BHP Billiton declined to comment on the report.
At 11.07am shares in BHP Billiton were trading 2.28 percent or 4.84 rand lower at 207.74 rand on the JSE.