By JILL LAWLESS
LONDON (AP) — Northern Ireland’s second-biggest political party has blocked the formation of a working Belfast legislature, deepening political deadlock over post-Brexit trade rules. The Democratic Unionist Party came second in a Northern Ireland Assembly election last week that saw Irish nationalist party Sinn Fein win the most seats. The new Assembly is due to meet Friday, but the DUP will block the election of a speaker, which means it can’t function. The DUP says it won’t take part unless border checks on goods moving to Northern Ireland from the rest of the U.K. are scrapped. The political deadlock is fueling a feud that could balloon into a trade war between Britain and the European Union.