PANAMA CITY, Feb 2 (Reuters) - The top diplomat in President Donald Trump's administration, Marco Rubio, began his first foreign visit on Sunday, meeting Panamanian President Jose Raul Mulino to discuss U.S. concerns about Chinese companies potentially affecting American shipping access around the Panama Canal and regional migration issues. The U.S. secretary of state is touring Central America and the Caribbean on his first foray in the post as he seeks to refocus U.S. diplomacy on the Western Hemisphere - in part to recruit help in stemming migration toward the U.S. southern border. Trump began his second term as president on Jan. 20. The visit also reflects a U.S. desire to counter China's growing diplomatic influence in Latin America. Trump upon returning to office threatened to take control of Panama Canal, built by the United States in the early 20th century and handed over to Panama under a 1977 Treaty, claiming the canal is being operated by China. The comments were followed by a public backlash, and Panama rebuked Trump's threats.