The United States is taking a German outcry over revelations of American spying on Europeans seriously, a U.S. lawmaker has said, ahead of his visit to Berlin Monday to soothe frazzled ties. Congressman Gregory Meeks told Handelsblatt business daily that U.S.-German relations were "of enormous importance" and must be stronger and closer still. "We want the Germans to know that we don't take their anger lightly," Meeks said in comments reported in German and made before his trip together with Senator Chris Murphy, who chairs the Foreign Relations Subcommittee on European Affairs. They were scheduled to meet the German foreign and interior ministers Monday before heading to Brussels Tuesday. Germans have reacted angrily to revelations that emails, phone calls, web searches and other data may have been hoovered up by U.S. intelligence agents, as part of widespread espionage that has also strained Washington's ties with other partners. It apparently included the tapping of Chancellor Angela Merkel's mobile phone by the U.S. National Security Agency, whose former contractor Edward Snowden has been the source of the leaks. After meeting the U.S. delegation Monday, Thomas Oppermann, the Social Democrats' parliamentary group leader and chairman of the secret service oversight committee, said the U.S. espionage affair was "not over". "We expect further light to be shed," he said, adding there had been agreement between the parties "that the completely out-of-hand practice of bugging by the NSA must finally have limits". Merkel called in parliament last week for answers over "grave" U.S. spying accusations which, she said, were testing transatlantic ties, including fledgling U.S.-EU trade talks. "We understand the German fears," Meeks said, adding that U.S. President Barack Obama was also "very concerned". "For this reason he's having checked which secret service methods are reasonable and which are not," he added.