If you are obtaining a VA or FHA loan in order to finance your purchase, you must include that information in your offer. This is because government loans place additional financial and performance obligations on the seller.
First, VA and FHA loans prohibit buyers from paying certain types of fees that are often charged by lenders, escrow companies, settlement agents, and title companies. They are called "non-allowable" fees. They still get charged anyway, but as the buyer, you are "not allowed" to pay them. The result is that the seller ends up paying them instead of you.
Most of these "non-allowable" fees come from your lender. By the time you are making an offer you should have already been pre-qualified by a loan officer, so you or your real estate agent can ask how much the lender's non-allowable fees will be. Experienced agents should also have an idea of what non-allowable fees will be charged by the escrow or settlement agent and the title insurance company.
Since these are fees the seller would not pay on an offer with conventional financing, this information must be included in your offer. You should also realize that since the seller will be paying these additional fees, they may be a little less negotiable on the price.