When you want to express a strong and confident statement, you may use the word "asseverating." However, sometimes you need to be creative in your language use and try out different synonyms to keep your writing fresh and varied. Other terms you can use to convey a similar meaning include declaring, affirming, avowing, asserting, stating, maintaining, professing, or pronouncing. Each word has its nuances and distinctions, so you may want to choose the most appropriate one to match the intended tone and context of your message. By expanding your vocabulary and using synonyms, you can bring more color and expression to your writing.