Eugene (United States) (AFP) - Anouk Vetter of the Netherlands leapfrogged Belgium's two-time Olympic champion and overnight leader Nafi Thiam with one event left to race in the heptathlon on Monday.
Thiam was the overnight leader with 4,071 points, 61 ahead of Vetter.
Monday saw Thiam manage the furthest long jump of the field, going out to 6.59m to consolidate her lead, Vetter managing a credible 6.52m.
Then came the javelin, however, where the Dutch athlete threw a massive 58.29m while Thiam could only get 53.01.
It was enough to put Vetter in the lead, on 6,045pts, 19 ahead of Thiam.
There is just the final, strength-sapping 800m to race, scheduled for 0155 GMT, to wrap up the gruelling two-day multi-discipline event.
Vetter, the reigning Olympic silver medallist, has a personal best of 2:17.71 while Thiam's fastest two-lap time is 2:15.24, set in 2016 and 2017 respectively.
The closeness of their 800m times means the heptathlon will go down to the wire.
Reigning world champion Katarina Johnson-Thompson of Britain sat in eighth on 5,387pts.
