WASHINGTON - President Clinton and European Union leaders held a summit at the White House on Friday, but they failed to resolve U.S. concerns over European Union plans to prohibit imports of products containing "specified risk materials" and the EU's slow approvals process for genetically modified crops.

The two issues were on the agenda at the Ninth Biannual U.S.-EU Summit, attended by European Commission Chairman Jacques Santer, Vice Chairman Leon Britten, and Jean-Claude Juncker, the prime minister of Luxembourg.