She will not announce an endorsement on Wednesday, the Wall Street Journal reported, but will encourage Trump to earn the support of Republican and independent voters who backed her.
Haley was Trump's last remaining rival for the Republican nomination.
On Super Tuesday Trump won the Republican votes in 14 of 15 states - including delegate-rich California and Texas – brushing aside Haley, whose only win of the night came in Vermont, Reuters reported.
Haley was expected to emphasize that she will continue to advocate for the conservative domestic and foreign policies she supports and caution against some of the dangers, such as isolationism and a lack of fiscal discipline, that she sees coming from Washington.