Sydney - US private equity firm Kohlberg Kravis Roberts on Monday upped its bid for Australia's Treasury Wine Estates by 10.6 percent, valuing the company at Aus$3.38 billion (US34 billion).

Treasury Wine Estates, which has assets on three continents with more than 80 brands, in May rejected a Aus$4.70 a share offer, arguing it undervalued the company.

The US firm bumped up its offer to Aus$5.20, with the Australian company saying it was now in negotiations for due diligence of its books.

The revised offer pushed Treasury Wine Estates shares four percent higher to close at Aus$5.15.

The firm has more than 11,000 hectares (27,000 acres) of vineyards, sales of 32 million cases of wine annually and employs 3,500 people.

Its key products in Australia include the Lindeman's, Wolf Blass and Rosemount brands and the Beringer and Chateau St Jean labels in the United States. - Sapa-AFP