Saudi National Bank, the kingdom's biggest lender, has set the spread for its benchmark-sized 5-year sukuk, or Islamic bond, an arranging bank document showed on Tuesday.

The spread for the debt sale was set at 90 basis points over U.S. Treasuries, tighter than the initial guidance of 120 bps over the same benchmark earlier in the day, after the orderbook topped $4.1 billion, the document said.

(Reporting by Shamsuddin Mohd; Editing by Kevin Liffey)