By Ted Hesson WASHINGTON (Reuters) – The United States will extend expiring work permits for a year and a half for tens of thousands of immigrants due to lengthy backlogs to process renewals, U.S. Citizenship and Immigration Services (USCIS) said on Tuesday. The change, outlined in a temporary final rule set to take effect on Wednesday, will prevent up to around 260,000 immigrants from losing work authorization over an 18-month period and give USCIS time to clear the queue of applicants, the agency said. Immigrants applying to renew work permits who normally qualify for an automatic 180-day ex…