Mexico's América Móvil SAB de CV late Thursday, June 21, said it had yet again increased its stake in Royal KPN NV, highlighting the Dutch telecom's apparent inability to fend off its peer's unwanted bid for a minority stake.

América Móvil, of Mexico City, said it increased its KPN stake to 20.9% from 8.7% by buying shares both on the market and in private deals.

KPN has hired Goldman, Sachs & Co. and J.P. Morgan Chase & Co. to help it defend against the Mexican company's advances but has had no success yet in finding a white-knight bidder or securing asset sales that would help it ward off the suitor.

On Wednesday KPN said it had been unable to find a buyer for its German E-Plus division and on Thursday it put its Belgian BASE unit, which is expected to bring in €1.8 billion ($2.26 billion), on the block.

América Móvil, owned by the world's richest man, Carlos Slim, in April said it wanted to buy just under 28% of KPN at €8 per share to reach across the Atlantic. KPN's stock has yet to reach that level and by late Friday morning had slipped 4.5%, or €0.33, to €7.15 as the Dutch company's options to defend against the deal dwindled.

América Móvil has since lined up a deal to buy 23% of Telekom Austria AG, but analysts said it may eventually seek majority stakes in its investment targets. The KPN offer intentionally avoids giving the company more than 30% of the Dutch rival since cresting that threshold would require it to launch an offer for the entire company.

"América Móvil's strategy is unclear but that doesn't mean it's necessarily bad," wrote UBS analyst Nick Lyall in a note. He has a neutral rating on the stock.

The KPN offer expires June 27.