BEIRUT, April 26, 2018 (Reuters) - Lebanese will have a first opportunity in nine years to vote in a general election on May 6 under new rules, expected to bring some changes to parliament but preserve a unity government combining its main political blocs. A smooth election and the swift formation of a new government are not only important for Lebanon's political stability but also to bolster a weak economy that is in dire need of reforms and investment. The new voting system has generated uncertainty in some districts, but Prime Minister Saad al-Hariri looks likely to form another unity government that includes Iran-backed Shi'ite movement Hizbollah. Though Hariri is expected to remain the biggest Sunni figure in parliament and keep his job, many analyses predict his parliamentary bloc will lose seats. Hizbollah may emerge stronger, though there is little prospect of it and its allies securing the two-thirds majority needed to dominate the state. Hariri has called for a new government to be formed swiftly to press ahead with reforms to put public finances on a sustainable path. Otherwise donors may withhold $11 billion in soft loans pledged in April to help revive the economy. Most parties in Hariri's coalition government are likely to rejoin, but those which win more seats may demand more posts in cabinet or more important portfolios like the finance ministry. Last time Lebanese voted for a new parliament in 2009, Hizbollah and its allies campaigned in a "March 8" bloc against Hariri and his allies in a "March 14" bloc.