The European Union and the United States have agreed that addressing global warming is a pressing matter. President George W Bush acknowledged the need to persuade Russia on the importance of a missile shield in Europe. During a White House summit with German Chancellor Angela Merkel and European Commission President Jose Manuel Barroso, they also expressed their strong commitment to finalizing a global trade agreement as part of the Doha round of talks. The leaders maintained pressure on Iran to abandon its pursuit of nuclear weapons despite Tehran's defiance of US-EU demands to halt uranium enrichment. Merkel, on her first visit to Washington as the EU president, emphasized the importance of addressing global climate change ahead of the upcoming Group of Eight summit in Germany. During a shared press briefing in the Rose Garden, the European representatives expressed satisfaction with the progress made on the issue, even though specific actions for the EU and the US to collaborate on addressing the problem were not outlined. Barroso stated, "I am pleased to see progress in this meeting. We acknowledge the existence of a significant global threat and the necessity to decrease emissions. We concur on the importance of working together." Bush, who was criticized for being slow to acknowledge climate change as a problem, emphasized that any agreement between the United States and Europe would not have a significant impact unless developing countries like China were included. He explained that even if the United States completely stopped emitting greenhouse gases, China could easily produce the same amount within a short period of time. However, Merkel argued that it is the responsibility of developed countries to take the lead in reducing carbon emissions. She stated that without action from developed countries, it would be difficult to persuade other nations to follow suit and reduce worldwide CO2 emissions. The leaders of the US and EU met amidst criticism from Russia regarding US plans for a missile shield in Eastern Europe. Russian President Vladimir Putin vowed to take action against the system. President Bush mentioned that German Chancellor Angela Merkel had previously voiced concerns about the missile shield and suggested he explain his vision to Putin. To address this, Bush sent Defense Secretary Robert Gates to Moscow to offer Russia the chance to participate in the shield, which is meant to counter terrorist threats rather than reignite the Cold War. Bush expressed hope that the dialogue with Russia would clarify intentions and show that the US is not an adversary, but a friend.