German Chancellor, Angela Merkel has told Russian President, Vladimir Putin that the planned referendum on the future of the Crimean peninsula would be a violation of the Ukrainian constitution and international law, a German government spokesman has said, Anadolu Agency reports.

“The Chancellor strongly underlined Germany’s position,” government spokesman, Steffen Seibert said in a written statement after a telephone call between the two leaders. “The so-called referendum in the Crimea set for 16 March is illegal,” Seibert stressed. “Holding this referendum is against the Ukrainian constitution and international law.”

The German chancellor has also expressed regret for the lack of progress in efforts to establish an “International Contact Group,” which was proposed by Germany last month to find a political solution to the Ukrainian crisis. Merkel underlined the urgent need to make progress in these efforts, Seibert added.

The planned referendum has been condemned as illegal by the European Union and the United States.