NEW YORK (Reuters) - U.S. 30-year mortgage rates rose for a second straight week to their highest levels since late December in step with a jump in Treasury yields, according to mortgage finance agency Freddie Mac <FMCC.PK> on Thursday.

The borrowing cost on 30-year mortgages, the most widely held type of U.S. home loan, averaged 4.30 percent in the week ended March 16, which was the highest since 4.32 percent in the week ended Dec. 29 and was above 4.21 percent the preceding week, it said.

(Reporting by Richard Leong)