BERLIN, Dec 15 (Reuters) - A German warship sailed into the South China Sea on Wednesday for the first time in almost 20 years, a move that sees Berlin joining other Western nations in expanding its military presence in the region amid growing alarm over China"s territorial ambitions. China claims almost the entire South China Sea as its own, despite an international tribunal ruling that Beijing has no legal basis for these claims, and has built military outposts on artificial islands in the waters that contain gas fields and rich fishing. The German navy vessel has begun the transit through the South China Sea on its way to Singepore that is expected to take several days, a spokesperson for the defence ministry in Berlin said on Wednesday. The frigate Bayern is the first German warship to cross the South China Sea since 2002, waters that 40% of Europe"s foreign trade flows through. The U.S. Navy, in a show of force against the Chinese territorial claims, regularly conducts so-called "freedom of navigation" operations in which their vessels pass close by some of the contested islands. China in turn objects to the U.S. missions, saying they do not help promote peace or stability. Washington has put countering China at the heart of its national security policy and seeks to rally partners against what it says are Beijing"s increasingly coercive economic and foreign policies. Officials in Berlin have said the German navy will stick to common trade routes. The frigate is not expected to sail through the Taiwan Strait either, another regular U.S. activity condemned by Beijing. Nevertheless, the former German government made it clear the mission serves to stress the fact Germany does not accept China"s territorial claims. Germany is walking a tightrope between its security and economic interests as China has become Berlin"s most important trading partner. German exports there have helped mitigate the impact of the COVID-19 pandemic on Europe’s biggest economy. Countries including Britain, France, Japan, Australia and New Zealand, have also been expanding their activity in the Pacific to counter China"s influence.