The increasingly aggressive and assertive maneuvers by China’s military , the People’s Liberation Army (PLA), is a “major problem,” according to a top Pentagon official.

Ely Ratner, the assistant secretary for the Indo-Pacific, said the department had seen “a steep rise in the region of PLA aerial intercepts in particular” over the last 18 months, which he described as “more assertive, aggressive, unprofessional, risky, [and] unsafe behavior by the PLA.”

His comments, which he made Thursday at a Center for a New American Security conference, came in the aftermath of two similar incidents in recent weeks, one of which was an aerial intercept, while the other was a naval one in the Taiwan Strait.

The Pentagon released footage of both incidents, which showed Chinese aggression. In the aerial intercept, a Chinese aircraft was shown flying in front of an Air Force RC-135, forcing it to fly through its turbulent wake . In the second incident, a Chinese naval ship twice sailed in the way of U.S. and Canadian naval ships the U.S. said were operating within international law.

“A U.S. naval ship operating with, in this instance, Canada, an ally in accordance with international law, and it was a very dangerous maneuver by the PLA Navy,” Ratner explained. “That's not two ships almost colliding. That's one ship almost colliding with another operating in accordance with international law.“

Earlier this week, White House National Security Council coordinator John Kirby said these incidents "have happened with more frequency than we'd like," adding, "There was absolutely no need for the [People's Liberation Army] to act as aggressively as they did. It won't be long before somebody gets hurt. That's the concern with these unsafe and unprofessional intercepts. They can lead to misunderstandings. They can lead to miscalculations."

Secretary of Defense Lloyd Austin briefly met with Chinese Minister of National Defense Li Shangfu at the Shangri-La summit in Singapore last week but it was not a substantive conversation, and the Chinese ministry denied a request for a more formal conversation, which is in line with their response to similar requests dating back months.

The Chinese have largely ignored outreach by U.S. military officials dating back to early this calendar year when following the Chinese spy balloon that traversed the continental United States, including over sensitive military targets, in late February before being shot down over the Atlantic Ocean.

The Pentagon views China as its "pacing challenge," and describes the People's Liberation Army or PLA as the only power that has the intent and capability to reshape the international order in its favor.

The Chinese have aggressively modernized and expanded their military in recent years, and are now on pace to have as many as 1,500 nuclear warheads by 2035, national security adviser Jake Sullivan said last week.

"The PRC has thus far opted not to come to the table for substantive dialogue on arms control. It has declined to share the size and scope of its nuclear forces or to provide launch notifications," the national security adviser said in a speech about the administration's plans to pursue nuclear arms treaties with Beijing and Moscow. "And it has not shown much interest in discussions regarding the changes it is making to its nuclear forces. Simply put, we have not yet seen a willingness from the PRC to compartmentalize strategic stability from broader issues in the relationship.”