Duffy Waldorf holds a twostroke lead after the fourth round of the $1.8 million Las Vegas Invitational on Saturday.

Waldorf, who started the day with a four-shot advantage, was in danger of frittering it all away when he took 40 strokes to negotiate the front nine on a windswept day at the Summerlin TPC.

However, he ran off eight pars and a birdie on the back nine on his way to a three-over-par 75.

Waldorf was at 16-under 272 with one round to play in the marathon 90-hole event, and fellow Americans Mike Reid (70), Bill Glasson (71) and Billy Mayfair (73) were two shots back.

Defending champion Tiger Woods shot a highly-creditable 71, eight shots behind.