Cuba maintains diplomatic relationships with several countries. Venezuela and Cuba have a strong alliance, with Venezuela exchanging 90,000 barrels of oil per day for Cuban medical specialists. This relationship has increased tensions with the United States. China has also strengthened economic ties with Cuba in recent decades, becoming Cuba's second largest trading partner through investments in industries like petroleum and agriculture. In contrast, the United States maintains a trade embargo and has been unwilling to restore full diplomatic relations with Cuba since the 1959 revolution.