LONDON — The United States pressed Argentina to end its investigation of Iranian complicity in the 1994 bombing of a Jewish center in which nearly 100 people were killed. Western diplomatic sources said the administration of President Barack Obama urged Argentina on several occasions to either stop or limit the investigation into the bombing of the Argentine-Israeli Mutual Association in Buenos Aires. The sources said the U.S. appeals marked one of the demands by Iran for a reconciliation with Washington. “Argentina had hard evidence against at least one Iranian leader, which prevented him from traveling abroad,” a source said.