By John O'Donnell FRANKFURT (Reuters) - The European Central Bank's decision to support Greece's shuttered banks by keeping its emergency funding line open gives the country's lawmakers a few days to seal reforms for an aid deal to keep it in the euro. The lawmakers' support for tough reforms, agreed by leftist Prime Minister Alexis Tsipras on Monday after all-night talks, is crucial for starting the next phase of negotiations on a tentative aid deal, that will potentially unlock funds to help Greece make the roughly 3.5 billion euros (2.5 billion pounds) ECB debt repayment. Missing that payment would likely force the ECB to turn off the 89 billion euro Emergency Liquidity Assistance that it agreed to extend again on Monday.