Unless both buyers and sellers have signed the Purchase and Sale agreement, there is no binding agreement yet between the two parties.
Your realtor can express your intention to the listing agent that you have an offer--which should be more attractive than the offer on the table or the offer the seller is considering. The terms of the offer of the other buyer can be withheld or held confidential.
However, the decision resides in the seller if they would like to have your offer get submitted before accepting the other offer.
The listing agent's job is to get the best offer for the seller client. They might counter all offers for final and best.
Best of Luck.