Hundreds of rocky islands, islets, sandbanks, reefs and cays lie scattered across Asia’s eastern waters, unimportant-looking to the naked eye but significant enough to spark what may be the most worrying deterioration in U.S.-China relations in decades.

China’s military rise, and its increasingly assertive claims to sovereignty over these largely uninhabited lumps of rock, coral and sand, have set it on a possible collision course with its neighbors, which also make various claims on the archipelagos, and with the United States, which has important alliances with three of the rival claimants and would be obliged to defend them in the event of an attack.

As Chinese and Vietnamese ships ram each other in the contested waters, and Chinese and Japanese fighter jets play games of chicken in Asia’s disputed skies, the risk of military escalation is growing. Even more significantly, the standoff is generating bad blood between Washington and Beijing and could torpedo cooperation on important global issues, including the Middle East, climate change and nuclear proliferation.

Secretary of State John F. Kerry and Treasury Secretary Jack Lew will visit Beijing on Wednesday and Thursday for the sixth annual Strategic and Economic Dialogue. And while Washington has been focused more on Iraq, Syria, Ukraine and Russia, some say the U.S.-China relationship is facing its stiffest test since President Richard M. Nixon traveled to Mao Zedong’s China in 1972.

“U.S.-China relations are worse than they have been since the normalization of relations, and East Asia today is less stable than at any time since the end of the Cold War,” said Robert Ross, a political science professor at Boston College and associate of Harvard’s John King Fairbank Center for Chinese Studies.

The Chinese government released video that purports to show Japanese fighter planes flying dangerously close to a Chinese fighter planes over the disputed waters of the East China Sea. (Defense Ministry of China)

The Obama administration’s foreign policy rebalance, or

“pivot,” to Asia has been widely interpreted in China as an attempt to contain its rise.

U.S. efforts to bolster ties with regional states such as Vietnam and to reassure nervous Asian allies such as Japan and the Philippines that it stands ready to defend them militarily have created a new narrative in Beijing — that the United States has encouraged China’s neighbors to push their territorial claims more aggressively.

“It is clear that the disputes are between two sides, but the United States is taking sides, and it is not impartial,” Adm. Sun Jianguo, deputy chief of the general staff of the Chinese People’s Liberation Army, said in an interview.

In Washington, a rival narrative is taking hold: that China is intent on pushing its territorial claims through the threat of military force and that it ultimately wants to push the United States out of Asia.

There have been more intense crises in U.S.-China relations, including the fallout from the 1989 Tiananmen Square massacre of pro-democracy protesters, but none, perhaps, as fundamental and structural as this.

In November, China spooked its neighbors by announcing an air defense identification zone over the East China Sea, including over islands administered by Japan.

In March, the Chinese coast guard tried to block Philippine vessels from resupplying soldiers stationed on the disputed Second Thomas Shoal. Two months later, it deployed a $1 billion deep-sea oil drilling rig into disputed waters off the Vietnamese coast. It has also been building artificial islands in the South China Sea that U.S. officials say are meant to enhance its stance on sovereignty.

China says it has historical claims to a huge swath of the South China Sea, but its recent assertiveness has puzzled experts, appearing to undermine last year’s efforts to promote a more cooperative, development-focused relationship with its neighbors.

Some argue that President Xi Jinping may see external threats as useful in ushering in tough reforms, including of the military; others say that China is simply baring its fangs as it seeks to build a new Asian order in which it, not the United States, is the major player in the region.

Most agree, though, that China is asserting itself partly because it now possesses a modern deep-water navy and professional coast guard.

Whatever the reason, China’s rise has left the United States caught between its commitments to allies and its desire to maintain a constructive relationship with China. In recent months, it has seemed to emphasize the former, sending B-52 bombers to fly through China’s air defense zone and threatening to reevaluate its military posture in Asia if China extends the zone to the South China Sea.

In April, President Obama visited U.S. allies Japan, South Korea and the Philippines in a trip that pointedly excluded China. While in Japan, he became the first president to explicitly say that the U.S. defense treaty covered islands administered by Japan. In the Philippines, he signed a new 10-year defense agreement.

There has been an equal and opposite reaction from Beijing. When U.S. Defense Secretary Chuck Hagel implicitly accused China in May of “intimidation, coercion or the threat of force” in asserting its territorial claims and warned that the United States “will not look the other way when fundamental principles of the international order are being challenged,” Lt. Gen. Wang Guanzhong called Hagel’s comments “excessive” and “suffused with hegemony, incitement, threats and intimidation,” China Central Television reported.

Daniel Russel, assistant secretary of state for East Asian and Pacific affairs, argues that the blunt exchanges between the countries could be beneficial.

“It is an indication of health, I believe, that we are able to be so direct with China, without fearing that we are tanking the relationship or the prospects for cooperation,” he said in an interview. “We do not pull our punches, but at the same time, we are working hand in hand in China wherever we can.”

Some critics say that the United States should have been more assertive in forging closer economic links with Asia through a Trans-Pacific Partnership trade deal and with China through a bilateral investment treaty.

“We need a lot more weight on the economic side, because that’s what keeps your relationship from tipping into a Cold War relationship,” said Christopher Johnson of the Center for Strategic and International Studies.

Also fueling China’s adventurism is a feeling among some Chinese officials that the United States is inconsistent and lacks resolve. They point to the administration’s unwillingness to punish Syria for using chemical weapons and its failure to prevent the Russian move into Crimea as showing it to be a “paper tiger,” said Johnson, the CIA’s former top China analyst, who is in regular contact with Chinese officials. “They believe Obama is fundamentally weak and disinterested,” he said.

But, Johnson added, Beijing would be wrong to underestimate the U.S. commitment to defend Asia. “America is a sleeping giant,” he said, “and if you prod us too hard, we are going to mobilize.”

Either way, foreign policy experts agree that the relationship deserves much more attention than it is getting. Kerry is widely seen as more interested in the Middle East, while national security adviser Susan E. Rice has yet to visit Beijing, leaving China policy without a sufficiently senior voice in Washington. Meanwhile, Obama’s refusal to visit China for a return version of last year’s Sunnylands summit in California with Xi has also “personally irritated” his Chinese counterpart, Johnson said — although he is scheduled to visit Beijing for an Asia-Pacific summit in November.

With that visit, at least, and with this week’s Strategic and Economic Dialogue, the administration has a chance to focus minds on one of its most serious foreign policy challenges, experts say. “Summits,” said Ross, of Boston College, “have the value of making presidents pay attention.”

Gu Jinglu contributed to this report.