May 10 (Reuters) – A federal judge on Wednesday urged the U.S. Securities and Exchange Commission to resolve its dispute with law firm Covington & Burling over the agency's demand for the names of 300 clients affected by a cyberattack on the firm. But both sides indicated during the hearing in Washington, D.C., that a court order would be necessary to break the impasse. The SEC sued Covington in January to force the prominent Washington-based firm to identify public company clients whose information was accessed or stolen in the breach. The hack was carried out by the Chinese-linked Hafnium cyber-espionage…