Angela Merkel has become the first German leader to address a joint session of the US Congress.The newly-re-elected Chancellor thanked America for the role it played in helping bring down the Berlin Wall, 20 years ago. Now, she said new tests lie ahead. “Today our generation of politicians has to show it can solve the challenges of the 21st century, that they can tear down today’s walls in our heads,” said Merkel, fresh from a meeting with President Obama. “This means – bringing peace and security, ensuring prosperity and equality and saving the planet.” In a speech punctuated by standing ovations, she stressed Germany’s ongoing commitment to Afghanistan and said Iran must be prevented from obtaining a nuclear weapon. She also told Congress there was “no time to lose” in the fight against climate change. “We need an agreement at the climate conference in Copenhagen in December,” said Merkel. “We need an agreement on one objective – global warming must not exceed two degrees Celsius. To achieve this, we need the readiness of all countries to accept internationally binding obligations.” Merkel’s speech had a strong personal touch as she shared her memories of growing up in East Germany, behind what was then the Iron Curtain. .