The adventure sequel starring Nicolas Cage should overtake the $173m lifetime total of its 2004 predecessor by the end of Monday.
Warner Bros' I Am Legend climbed to second place on $16.3m for $228.6m after four, while Fox Searchlight's Juno continued its excellent run as it jumped two places to third on $16.2m for $52m.
Juno is charging toward the $59.9m lifetime total of Little Miss Sunshine and Searchlight's biggest grossing release, Sideways, which ended on $71.5m.
Fox's Alvin And The Chipmunks fell two to fourth on $176.7m after four while Warner Bros' horror title One Missed Call was the only new release to break into the top 10, ranking fifth on $13.5m. Edward Burns stars in the remake of the J-horror about a mysterious chain of calls to mobile phones that herald imminent doom for the recipient.
Focus Features' acclaimed drama Atonement expanded into more theatres and surged four places to 10th in the fifth weekend as $5.1m raised its tally to $19.2m.
The Weinstein Company's drama The Great Debaters, which is being handled domestically through MGM, ranks 12th in its second weekend and has amassed $22m.
Overall box office painted a rosy picture as the top 12 titles combined for $123.9m and climbed 18.5% against the first weekend of 2007.
Estimated Top 10 North America Jan 4-6, 2007
Film (Dist)/Int'l dist/Est wkd gross/Est total to date
1 (1) National Treasure: Book Of Secrets (Buena Vista) WDSMPI $20.2m $171m
2 (3) I Am Legend (Warner Bros) WBPI $16.3m $228.6m
3 (5) Juno (Fox Searchlight) Fox Int'l $16.2m $52m
4 (2) Alvin And The Chipmunks (Fox) Fox Int'l $16m $176.7m
5 (-) One Missed Call (Warner Bros) WBPI $13.5m -
6 (4) Charlie Wilson's War (Universal) UPI $8.2m $52.6m
7 (7) P.S. I Love You (Warner Bros) Summit $8m $39.4m
8 (8) The Water Horse: Legend Of The Deep (Sony) SPRI $6.3m $30.9m
9 (9) Sweeney Todd (DreamWorks-Paramount) WBPI $5.4m $38.5m
10 (14) Atonement (Focus Features) UPI $5.1m $19.2m