This will vary between jurisdictions but my understanding is that, yes, you can be sued for making a false promise to buy from a specific seller even if you don't get to the stage of a formal contract.

Putting out a press release, or RFP, saying 'we want to buy X quantity of Y' without the intent to follow up isn't illegal. However, getting to the point of a handshake agreement with a specific vendor but then backing out means that you will be expected to pay compensation even though no formal contract was signed.