Leeds have been tracking attacking midfielder De Paul since last summer.
But Marcelo Bielsa is in two minds whether to bid in January or make a final decision before the start of next season.
However, champions Liverpool have now made their interest known.
And that could force Elland Road bosses to accelerate their plans and try to buy the Argentine during this window.
De Paul has flagged up well on Liverpool's meticulous scouting system as they look to invigorate the squad in an attempt to stay ahead of their rivals in the Premier League.
Antonio Conte's Inter have also made it clear they would be interested in the 26-year-old.