Sandaza's current deal is due to expire at the end of the season and his agent recently hinted that he would not be signing an extension.
As a result, the 27-year-old will be allowed to join another club on a free transfer at the end of the season.
"Rangers want him to sign a pre-contract," Lomas told the Sunday Mail.
"If they want to get him now then they have to speak to me and make an offer.
"Hopefully Fran will be lining up against Rangers next week, not playing for them."
Sandaza joined St Johnstone last summer from Brighton & Hove Albion.