Together they represent 40 percent of all world trade and generate 60 percent of world growth. But although the European Union and the United States have much in common, great tensions exist between these two world powers. On Monday (April 30), at the U.S.-EU Summit in Washington, both sides will try to steer clear of a strong message on climate change and curbing greenhouse gas emissions. E.U. Vice President Margot Wallstrom said, "We might have to conclude that this is not the summit to go into details on exactly all of the issues that we both have in common and where we might diverge on climate change; but rather what is the new initiative for this summit and that is the economic partnership." That transatlantic partnership will be the focus of the Summit-- with both sides agreeing to remove costly non-tariff business barriers-- as part of a broad regulatory initiative. John Bruton is the EU's Ambassador to the United States said; "We want to make similar regulations on either side of the Atlantic. So that you don't have to test cosmetics twice for safety, test pharmaceuticals twice for safety, test cars twice for safety. That once you pass a test on either side your goods will be acceptable or your services would be acceptable on the other side." Nile Gardiner, a senior research fellow at the Heritage Foundation said, "There will be some movement on the issue of regulation here and transatlantic co-operation, however a much bigger question of course is U.S/EU trade and there has been very little movement in terms of the development of any coherent strategy between the U.S. and the EU with regard to trade subsidies." International issues -- such as Iran's nuclear program-- will also be on the summit agenda. But the way both sides confront the Iranian threat-- may expose further strains in the U.S.-E.U. relationship. Gardiner said that EU trade guarantees with Iran were an issue that would probably take much time. "European Union countries currently operate about ten billion dollars worth of export guarantees with regard to trade towards Tehran. Washington would like to see the European Union end those credit guarantees to end a wide array of investment portfolios inside Iran at this stage so I do see Iran dominating in terms of broader discussion with regard to the Middle East at this time," said Nile Gardiner. One issue both sides have agreed to keep off the agenda is the future of World Bank President Paul Wolfowitz. Although the European Parliament has called for his resignation over favours he arranged for a job employee-girlfriend, EU officials have said this is an issue for the World Bank and will not be discussed at the Summit.