The Pentagon confirmed to Newsweek that it warned China in advance about a test launch of a United States nuclear missile that was fired into the Pacific Ocean last week.

An unarmed Minuteman III intercontinental ballistic missile (ICBM) was launched by the U.S. Air Force on November 5 from Vandenberg Space Force Base in California. It flew about 4,200 miles to a test site within the Marshall Islands in the Central Pacific Ocean.

“The United States provided the PRC [People’s Republic of China] advanced notification of this launch to both the Ministry of Foreign Affairs and the Ministry of National Defense through U.S. Embassy channels in Beijing,” a Department of Defense spokesperson said.

The news that the U.S. military provided advance notice to China was first reported by Air & Space Forces Magazine on November 6. There is no formal agreement between the two countries that requires such a pre-launch notification, it said.

By sending this ad hoc notification, the U.S. hoped to encourage China to negotiate a pre-launch notification arrangement, according to the report. China inked a similar agreement with Russia in 2009, requiring them to pre-notify each other about ballistic missile launches.

“This pre-notification followed the PRC’s advanced notification of its September 25 ICBM test launch,” the Pentagon spokesperson told Newsweek. A DF-31AG ICBM was fired by the Chinese military from the South China Sea into the South Pacific Ocean at that time.

The Chinese military said “relevant countries” had been notified of the test in advance. The Pentagon later confirmed that it had received “some advanced notification” from China and praised this as a good thing as it prevented misperception or miscalculation.

Both the Minuteman III and the DF-31AG are capable of carrying nuclear warheads. The former has a 6,000-plus-mile range, while the latter can strike targets as far as 6,800 miles away.

The Chinese government acknowledged receipt from the American side in both cases, the spokesperson added. Both the Chinese foreign ministry and defense ministry in Beijing did not immediately return Newsweek‘s written requests for comment before publication.

Prior to the test, the U.S. Air Force announced that it had notified the Russian government, per existing bilateral obligations. In 2000, they signed a memorandum that reduced the possibility of a missile launch resulting from a false warning of a ballistic missile attack.

“There’s nothing that prevents the United States, Russia, and China from notifying each other about upcoming missiles tests,” Hans Kristensen, director of the Nuclear Information Project at the Federation of American Scientists (FAS), told Newsweek. “In fact, common sense should make them do so voluntarily, even if the political climate makes a formal agreement unlikely. Communication and cooperation are good.”

Liu Pengyu, a spokesperson for the Chinese embassy in the U.S., told Newsweek that China is willing to uphold the principles of mutual respect, peaceful coexistence, and win-win cooperation, maintain communication and cooperation with the U.S., “so as to enhance mutual understanding, avoid misunderstanding and misjudgment, and jointly manage risks.”

However, experts say China remains skeptical of the benefits of transparency with its rivals. The U.S. has labeled the country as its only competitor with both the intent to reshape the international order and the economic, diplomatic, military and technological power to do it.

China is concerned that such measures could lead to “negative security consequences” if sensitive military information about its technologies were disclosed, Tong Zhao, a senior fellow at the Carnegie Endowment for International Peace, explained to Newsweek.

Given Beijing’s reluctance, China and the U.S. could still achieve significant benefits by adopting what he called “voluntary, reciprocal practices.” This would provide pre-launch notifications for space or missile activities that pose the highest risk of misinterpretation.

“Once China becomes more comfortable with these informal practices, a more formalized agreement might become more feasible.” He added that an agreement with the U.S. could serve China’s interests by building confidence and reducing the risk of misunderstandings.

The U.S. also tried to encourage China to subscribe to the Hague Code of Conduct, which requires members to voluntarily commit themselves to providing notifications of ballistic missile and space-related launches.

The U.S. and China are among the nine nuclear-armed countries in the world. According to government data, the American nuclear stockpile consisted of 3,748 warheads as of September last year.

The Bulletin of the Atomic Scientists estimated that up to 800 nuclear warheads were assigned to the U.S. ICBM force, of which half were deployed on 400 Minuteman IIIs.

China has never officially revealed the size of its nuclear arsenal. The U.S. military estimated last year that the country possessed over 500 nuclear warheads, and the number would probably be over 1,000 by 2030 as it continued a rapid nuclear expansion.