WASHINGTON- US Vice President Biden told Ukrainian President Petro Poroshenko in a call on Friday that the United States is prepared to move forward with a third loan guarantee agreement to support reforms, the White House said. The third $1 billion loan guarantee was promised in November, but was contingent on progress on fighting corruption and on reforms. Biden also welcomed the appointment of a new prosecutor general in Ukraine as 'an important first step to bringing much needed reform,' to the prosecutor general office.