JERUSALEM  - Israeli police have sent two senior investigators to the United States to expand a corruption probe linked to embattled Prime Minister Ehud Olmert, a spokesman said on Sunday. "Two senior officials from the police's fraud department, Lior Rice and Tzahi Habekin, are in the United States for two and a half weeks to continue the corruption investigation involving Prime Minister Ehud Olmert," police spokesman Micky Rosenfeld told AFP. He added that the two detectives would seek to obtain documents from several US banks and companies related to a corruption investigation into financial contributions given to Olmert before he became premier. The corruption probe, the most serious of four pending investigations involving the increasingly unpopular premier, is focused on donations given to Olmert by the Jewish-American financier Morris Talansky. Talansky testified in May that he had given Olmert at least $150,000 in the 14 years before he became prime minister in 2006, some of which might have been used to fund Olmert's taste for luxury goods. The expanding corruption probe brought widespread calls for Olmert to step down or hold a primary to select a new head of his centrist Kadima party. On June 25 Olmert narrowly averted an Opposition bid to bring down the government by cutting a deal with the Labour party, a crucial coalition partner, that requires Kadima to hold primary elections by September 25. The party leadership is scheduled to meet by July 10 to fix a date for the primaries, which are expected to pit Foreign Minister Tzipi Livni against Transport Minister Shaul Mofaz and possibly Olmert as well.