May 21 (Reuters) - Shares of Australia's BHP Group touched a three-month high on Tuesday, ahead of a deadline to lodge a formal bid for rival Anglo American, which rejected its sweetened $43 billion takeover proposal last week.

Under the UK takeover rules, BHP has until 1700 GMT on Wednesday to make a binding bid for Anglo American or it will be forced to walk away for at least six months. If the companies find an agreement in the meantime, an extension can be granted.

London-listed Anglo has rebuffed BHP twice, saying its proposals continue to significantly undervalue the company.

Both of BHP's all-share takeover offers required that Anglo divest its platinum and iron ore assets in South Africa, where it employs more than 40,000 people.

BHP's latest offer was for 27.53 pounds ($34.99) per Anglo share, up from 25.08 pounds previously.

Last week, Anglo laid out plans to refocus its company on copper while spinning out or selling its less profitable coal, nickel, diamond and platinum businesses, as it moved to fend off BHP.

Shares of BHP, the world's largest listed miner, rose as much as 0.8% to A$46.09 on Tuesday, their highest since Feb. 20.

Anglo's London-listed shares closed up 0.1% at 26.80 pounds on Monday.

($1 = 0.7869 pounds) (Reporting by Himanshi Akhand in Bengaluru; Editing by Rashmi Aich)