Sept. 15 (Bloomberg) -- Italian Deputy Prime Minister Gianfranco Fini threatened to block a proposed electoral law backed by Italian Prime Minister Silvio Berlusconi, underscoring divisions within the ruling coalition less than a year before national elections. Fini made the threat after the Union of Christian Democrats said they would seek to amend the draft legislation announced two days ago to eliminate a 4 percent threshold for parties to be given seats in parliament. Fini backs the voting limit to exclude marginal parties from gaining seats in legislature. ``What is essential is that the electoral law safeguard the bipolar system,''...