Helsinki I NPR's Mara Liasson reports from Helsinki, Finland, where the presidents of the United States and Russia have begun their summit meeting. Tonight, the main event was an informal dinner. Tomorrow, Bill Clinton and Boris Yeltsin sit down to talk about NATO. President Clinton's position will be that NATO should expand eastward to include countries in eastern and central Europe. President Yeltsin's position will be that any NATO expansion is a strategic mistake. Both sides are warning that there might not be much progress toward solving the problem.