LONDON, May 13 (Reuters) - BHP Group said on Monday that Anglo American had rejected a revised buyout offer valuing the company at 34 billion pounds ($42.67 billion).

Anglo American in April rebuffed BHP's $39 billion all-share takeover proposal, saying it was opportunistic and significantly undervalued its prospects.

"BHP is disappointed that the Anglo American Board has chosen not to engage with BHP with respect to the Revised Proposal and the improved terms," it said in a statement.

"BHP continues to believe that a combination of the two businesses would deliver significant value for all shareholders," it added.

($1 = 0.7968 pounds) (Reporting by Clara Denina, Eva Mathews; Editing by Louise Heavens)