The German and French leaders called Monday for Russia and China to help increase pressure on Iran over its disputed nuclear program, and French President Nicolas Sarkozy said that Teheran must get "no nuclear weapon." Sarkozy recently has led European calls for tougher sanctions against Iran over its defiance of UN Security Council demands to halt uranium enrichment, which could be used both to generate nuclear power and create the fissile core of warheads. While France has suggested new European Union economic sanctions against Iran, Chancellor Angela Merkel has made clear that Germany wants to concentrate on negotiating sanctions at the UN. Merkel said after the two countries' Cabinets held a twice-yearly meeting that there was "a very great level of agreement" on Iran. The two have "the common position that, if Iran does not change its stance, further sanctions must be considered in the UN framework," she told reporters at the chancellery. "We want to have Russia and China in the world community that makes clear to Iran that we cannot resign ourselves to this nuclear program." Russia and China, both veto-wielding permanent members of the Security Council, so far have been skeptical about further sanctions, advocated by the United States and other Western countries. Sarkozy said that both Germany and France "believe in the usefulness of sanctions." "Germany and France think that, for sanctions to be efficient, there must be unity in the international community, including China and Russia, and that we must maintain the line of dialogue at the same time as firm sanctions," he said. "We may have a problem of pace here or there, but on the big picture of this policy we are on the same wavelength: no nuclear weapon for Iran," Sarkozy said. "The door remains open, but the sanctions are toughening." Both Sarkozy and Merkel have discussed Iran with US President George W. Bush during separate trans-Atlantic trips over the past week. Merkel has said she and Bush agreed that a diplomatic solution to the issue is still possible. Merkel stressed on Monday that European countries "want to reduce our own trade relations with Iran," noting the German government was restricting export guarantees and German banks had moved to halt business with Iran. Before their meeting at the chancellery, Merkel and Sarkozy went to a Berlin school to debate the challenges of integrating immigrants. Sarkozy, who has pushed legislation that institutes tests of language and fundamental French values, pressed home his argument that immigration needs to be controlled. "If we do not have the courage to master migratory flows, we will not succeed with integration," he said. "Our countries are open; they are not closed, they are not fortresses," he said. "But anyone who asks to come must respect the culture he wants to become his own." Berlin police said a 25-year-old man was detained after shouting insults at Merkel from the crowd after she visited the school with Sarkozy.