German Chancellor Angela Merkel congratulated US President-elect Joe Biden and said trans-atlantic ties were "irreplaceable", alluding to tensions during Donald Trump's leadership. "Congratulations!" Merkel said. "I wish luck and success from the bottom of my heart. "Our trans-atlantic friendship is irreplaceable if we want to overcome the great challenges of our times," she said in a tweet issued by a government spokesman. German Foreign Minister Heiko Maas welcomed Biden's election victory as a "new start" for transatlantic relations. "We want to invest in our cooperation (with the new president) for a new start in trans-atlantic relations, a 'new deal'," he tweeted, as Vice Chancellor Olaf Scholz hailed the opening of a "new chapter". On Wednesday German Defence Minister Annegret Kramp-Karrenbauer admitted that the German-US relationship had faced "a tough test in the past four years" with fierce Trump criticism of Berlin over trade and military spending. However, she said, "this friendship is more than a question of which administration is currently in the White House", saying she dismissed calls in Germany to "decouple ourselves from the United States". yap/smk/pvh/har