Mr Trump claimed Kirsten Gillibrand had come "begging" to him for donations and "would do anything" for cash.
Senator Elizabeth Warren said Mr Trump was "trying to bully, intimidate and slut-shame" her fellow Democrat.
Scores of Democratic congresswomen are urging Congress to investigate claims against the Republican president.
Three of his accusers held a press conference on Monday to repeat their allegations he groped, fondled, forcibly kissed and harassed them.
The Republican president has branded the accusations "fabricated" and "FAKE NEWS!"