Sept 4 (Reuters) - Holders Europe grabbed a 3-1/2 to 1/2 lead over the United States after the morning round of foursomes on the first day of the Solheim Cup at the Inverness Club in Toledo on Saturday. Clutch putts down the stretch by Europe"s Leona Maguire and Emily Pedersen helped Europe to their biggest lead after the first session of the biennial team competition since 2003. The U.S. need 14-1/2 points to win the competition while Europe need 14 to retain the trophy. The Americans lead the overall series 10-6. The three-day competition is expected to draw more than 100,000 fans to the newly renovated course and is scheduled to wrap up on Monday, the Labor Day holiday in the United States.