The Mexican telecoms giant America Movil upped the ante Thursday in its unsolicited bid for shares in Dutch peer KPN, saying it had managed to raise its stake in KPN to 20.9 percent. \"As a result of the transactions entered into today, both in and outside regular market trading,\" America Movil will hold more than 299 million shares in KPN \"representing a capital interest of 20.92 percent,\" a statement said. America Movil, which is controlled by billionaire Carlos Slim, launched its bid on May 30 for a 27.7-percent stake in the Hague-based KPN, offering eight euros ($10.07) a share or 2.6 billion euros in all. The Mexican telecoms operator held 4.8 percent of the Dutch group prior to making the hostile bid. KPN\'s board has urged shareholders to hold off on the unsolicited cash offer, saying that the deal substantially undervalued the Dutch operator. Meanwhile KPN managers raced to find an alternative source of cash for shareholders through the sale of two subidiaries, E-Plus and BASE. The Dutch group said Thursday that it would launch the sale of its Belgian mobile unit BASE next month now that a strategic review of the deal had been finalised. Although KPN did not say how much it wanted for BASE, local media reports in April, when KPN first said it was looking into a possible sale, quoted a figure of around 1.8 billion euros. \"The proceeds will be used to improve KPN\'s credit profile and financial flexibility,\" KPN said on Thursday, adding that BASE now accounted for about 19 percent of the Belgian market. Earlier this month the Dutch group said it would also look at \"strategic options\" for its German subsidiary E-Plus. According to the Dow Jones Newswires, KPN has held talks with Spanish telecoms Telefonica, but no agreement was reached because of \"current adverse conditions in financial markets,\" the Dutch group was quoted as saying. America Movil controls the mobile telephone market in Latin America with some 225 million clients in 18 countries at the end of 2010. In 2011, it posted the equivalent of 39 billion euros in revenues. The Dutch group employs 31,000 people and recorded sales of 13.16 billion euros last year.