(Reuters) - Elon Musk's artificial intelligence startup xAI has introduced Grok-3, the latest iteration of its chatbot, as it looks to compete with Chinese AI firm DeepSeek, Microsoft-backed OpenAI, and Alphabet's Google. Grok-3 debut comes at a critical moment in the AI arms race, just days after DeepSeek unveiled its powerful open-source model and as Musk moves aggressively to expand xAI's influence. The chatbot is being rolled out immediately to Premium+ subscribers on X, the social media platform owned by Musk. xAI is also launching a new subscription tier, SuperGrok, for users accessing the chatbot via its mobile app and...