Jamaica international Cummings, who was Rapids' leading striker in 2010, could link up with Villa until March when the Major League Soccer season begins.
Houllier said: "I see Omar getting better with every training session. I will make a decision about him soon."
cummings has been training with Aston Villa since 31 December and Houllier said that a work permit would be needed were he to be offered a loan deal.
It'd be nice if we do this with the option to buy, he could be the next American based player to have an effect in Europe
SoutWestVillain
Should he join Villa, Cummings will be following in the footsteps of Los Angeles Galaxy stars Landon Donovan,
who joined Everton on loan last term,
and David Beckham, who is currently
training with Tottenham Hotspur.
Cummings has played for the Rapids since 2007 and enjoyed a fine season in 2010, scoring 14 goals in 29 games and helping the side lift the MLS Cup.
Capped 13 times for Jamaica, Cummings played under John Barnes during the former Liverpool winger's tenure as manager, and was part of the Reggae Boyz Caribbean Cup title win in December 2010.
Premier League side Villa, who currently sit just above the relegation zone in 17th place, recently added £6m midfielder Jean Makoun to their squad.
Source: BBC Sport
Source: BBC Sport