Usually this is not a good idea. Often speaking fast will make your accent sound stronger. Here’s why:
There are specific rules that native speakers subconsciously follow when they speak quickly. If you don’t follow these rules your speech will be harder to understand. Americans reduce certain words and stress or emphasize certain others. This creates the rhythm of the language. Also, speaking faster might cause you to skip certain consonant sounds.
It’s better to speak slowly and clearly at first. Using a louder voice generally helps too. Then gradually increase the rate (speed) of your speech, making sure that you are still pronouncing every sound. Next, start linking the words. (connecting the final consonant of one word with the first vowel of the next word. For example, “move over” should sound like “moo vover”)
Be patient with your progress. Find good role models of speech. A TV newscaster or a radio talk show host would be good. Remember that not all Americans speak well.