German drug and chemical maker Merck KGaA has made an unsolicited bid for rival Schering AG ( SHR), according to media reports. Schering AG said Sunday it had received an all-cash bid of 77 euros, or about $91.78, a share from Merck KGaA. That¿s a 15% premium over Schering¿s 66.86 euro Friday closing price in Frankfurt. The Wall Street Journal estimated the offer¿s worth at around 15 billion euros, or $18 billion. Schering AG¿s U.S. shares finished Friday up $1.40, or 1.8%, at $79.70. Merck KGaA¿s offer appears designed to create the first big German drug maker capable of taking on global heavyweights in the pharmaceutical industry. The country¿s pharmaceutical companies are small and midsize. But Schering AG says it¿s not interested. "After the information about the approach became public, the executive board of Schering AG stated that this offer significantly undervalues Schering and its prospects as an independent specialized pharmaceutical company," Schering said, in a statement quoted by the Associated Press. Schering AG didn¿t characterize the bid as hostile but did call it unsolicited. The company said no negotiations are ongoing with Merck KGaA, according to the AP report. Merck KGaA has been entirely separate from New Jersey¿s Merck & Co. ( MRK) since the U.S. government confiscated the former subsidiary at the end of World War I. Similarly, Schering AG lost its connection to New Jersey-based Schering-Plough ( SGP) , during World War II.