Ties between the leaders of China and Russia

“The world system, and American influence in it, would be completely upended if Moscow and Beijing aligned more closely,” John Arquilla, a professor at the Naval Postgraduate School, wrote in the report, to which Defense Department officials and other analysts contributed.

The latest evidence of warming ties was a meeting last month in Moscow at which Mr. Putin thanked the Chinese leader, Xi Jinping, for enabling the two countries to do more than $100 billion worth of trade in 2018, up 30 percent from the previous year, and an implicit rebuke to America’s trade standoff with China. The two countries also signed more than two dozen agreements. That meeting came shortly after Mr. Xi called Mr. Putin his “best and bosom friend.”

The leaders have met almost 30 times since 2013. Russia recently agreed to sell China its latest military technology, including S400 surface-to-air missiles and SU-35 fighter jets.

While China and Russia have conducted joint military exercises intermittently for more than a decade, they began naval maneuvers in the Mediterranean in 2012 and last fall, staged what Russia called their biggest war games in decades in eastern Siberia. They plan to hold joint exercises on a regular basis in the future.

With melting ice opening new opportunities for oil and gas exploration, researchers from the two nations recently agreed to open a joint Arctic research center. They often vote alike at the United Nations and have similar positions on Iran and North Korea. Both have become much more active in the Middle East, where Russia is trying to regain its standing as a major power and China is trying to cultivate relations with energy suppliers like Iran.

The Pentagon white paper, and a separate report by the Center for Strategic and International Studies, warn that the United States and its allies are not moving fast enough to counter efforts by Russia and China to foment instability with “gray zone” tactics that fall short of military involvement — the use of proxy forces, political and economic coercion, disinformation, cyberoperations, and jamming technologies against American satellites.

In his State of the Nation address in February, Mr. Putin expressed confidence that ties with China would enhance Russian security and prosperity, especially as he aligns his Eurasian Economic Union plan with China’s ambitious Belt and Road Initiative, a colossal infrastructure program designed to link China with Asia, Africa and Europe.

Given its economic, military and technological trajectory, together with its authoritarian model, China, not Russia, represents by far the greater challenge to American objectives over the long term. That means President Trump is correct to try to establish a sounder relationship with Russia and peel it away from China. But his approach has been ham-handed and at times even counter to American interests and values. America can’t seek warmer relations with a rival power at the price of ignoring its interference in American democracy. Yet even during the Cold War, the United States and the Soviet Union often made progress in one facet of their relationship while they remained in conflict over other aspects.

The United States and Russia could expand their cooperation in space. The United States is already dependent on Russian rockets to reach the International Space Station. They could also continue to work closely in the Arctic, as members of the Arctic Council that has negotiated legally binding agreements governing search and rescue operations and responses to oil spills. And they could revive cooperation on arms control, especially by extending the New Start Treaty. It was encouraging that top State Department officials met their Russian counterparts twice in recent weeks, including in Geneva on Wednesday, although there was no immediate sign that the two sides made any progress on arms control or other major issues.

Given their history, China and Russia may never reach a formal alliance. The two have been divided by war and ideological rivalries and even now compete for influence in East Asia, Central Asia and the Arctic. Their contrasting trajectories would also make an alliance difficult. China is a rising power and the dominant partner; Russia is declining. China has the world’s second largest economy; Russia’s is not even in the top 10.

Still, their shared objectives could increase, further threatening Western interests. America needs to rally its democratic allies, rather than berate them, and project a more confident vision of its own political and economic model.