WASHINGTON (Reuters) - President-elect Joe Biden has called the $908 billion coronavirus aid bill taking shape in Congress a “downpayment” toward a bigger stimulus next year, but if it passes, that is all U.S. businesses and workers should count on, economists and political analysts say. There is likely to be little appetite among Republicans for supporting a second round of $1 trillion-plus spending after Biden takes office on Jan. 20 - a task that would be made more difficult if Republicans retain control of the Senate in Jan. 5 runoff elections in Georgia - said John Lieber, managing director of the Eurasia Group political risk consultancy. “If they do the full bipartisan $900 billion, then I think it’s a big ask to do anything new after Biden takes office,” said Lieber, a former adviser to Senate Majority Leader Mitch McConnell. Additional stimulus “would only become possible in a downside scenario where the vaccine rollout doesn’t go smoothly and the economy continues to drag well into 2021, leading to serious strains” on households, small businesses and local governments,” Lieber said. And even if Democrats take the Georgia seats, they would achieve a majority only with a tie-break vote from Vice President-elect Kamala Harris, leaving them far short of the 60 votes needed for most major spending legislation outside of normal budget reconciliation rules. Congressional leaders had hoped to unveil a near-term coronavirus aid package based on a $908 billion bipartisan proposal as early as Monday. Negotiations are hung up on differences over aid to state and local governments and COVID-19 liability protections for businesses. Moody’s Analytics Chief Economist Mark Zandi said members of Congress were under pressure to pass a stimulus bill now “because if they don’t, the economy is going to evaporate and that will be too much to bear politically.” He added that his baseline outlook for the economy assumes that Congress will pass “little of consequence” to stimulate economic growth after Biden takes office. As a result, it will take three full years - until the end of 2023 - to recover all of the jobs lost during the pandemic this year. By contrast, it took eight years to recover the jobs lost from the 2008-2009 Great Recession, another situation where Congress prematurely withdrew fiscal support, he said. Annual federal deficits had nearly doubled to the $1 trillion range during President Donald Trump’s term before the pandemic hit. After passing over $2 trillion in coronavirus-related stimulus earlier this year, a pivot back to fiscal restraint is “already starting to happen here in the middle of the pandemic,” Zandi said. Widespread distribution of the coronavirus vaccines is expected next spring, making Republican lawmakers reluctant to support another round of stimulus, said Michael Strain, director of economic policy studies at the American Enterprise Institute, a pro-business conservative think tank in Washington. Many will want to wait and see if the vaccine works and the economy starts to recover. In addition, Republicans, even if they lose control of the Senate, will be reluctant to give Biden an early victory, he said. "I expect that there will be difficulty in passing another economic stimulus measure in February," Strain told a Brookings Institution forum here last week. Democrats who hold out for a better deal after Biden takes office are likely making a "significant mistake."