Richard Nixon pursued a policy of détente to relax tensions with major communist powers. His national security advisor Henry Kissinger played a key role in negotiating diplomatic openings with China and the Soviet Union. In 1972, Nixon became the first US president to visit China, establishing diplomatic relations and acknowledging China's government. That same year, Nixon also visited the Soviet Union and negotiated the SALT I treaty, which placed the first limits on US and Soviet nuclear arsenals.