President Biden’s nominee for ambassador to China said Wednesday that reports of Beijing testing a nuclear-capable hypersonic missile are concerning and called for bipartisan cooperation on the issue and closer communication between American and Chinese officials to avoid military conflict.

Nicholas Burns, a veteran senior State Department official and Harvard professor, made the remarks during his confirmation hearing before the Senate Foreign Relations Committee, where he urged greater focus among the U.S., allies and partners over a Chinese nuclear buildup.

“We should all be concerned by the nuclear buildup in China, and that has to be a concern for allied nations as well as the United States,” Burns said.

Biden’s envoy to Beijing is likely to be one of the most consequential diplomatic postings, with the relationship between the U.S. and China at one of its lowest points since relations were first normalized in 1979, at odds on everything from trade to human rights to the future of the international order.

The president has identified China as the greatest national security challenge to the U.S. for the 21st century, and defined his administration’s policy as “strategic competition” – looking for the U.S. to outperform China economically and in technology and innovation and unite allies to push back on China’s crackdown on political opposition in Hong Kong, abuses in Tibet, and impose costs on Chinese officials complicit in the genocide taking place against Uyghur Muslims.

“The Biden administration is well and surely right to seek effective channels of communication with Beijing, to manage this competition responsibly, to diminish the risk of an accidental conflict and above all to maintain the peace,” Burns said.

“The United States has to proceed from a position of strength and pursue intense diplomacy in all these matters.”

Yet China’s apparent military provocations, including reportedly testing a nuclear-capable hypersonic missile in August and aggressive rhetoric and warplane flyovers of Taiwan, are raising the risk of conflict.

Burns said the press reports of the hypersonic nuclear-capable missile are concerning and that it reflects the attitude of the Chinese government in that “they don’t believe that they should be constrained in any way shape or form by arms control.”

He called for bipartisan unity to push back on Beijing’s nuclear ambitions.

“The Chinese have been saying for decades that they would like to have a minimum nuclear deterrence and they seem to be, quite rapidly, moving away from that older policy,” he said.

Burns, a two-time ambassador and who served as under secretary of State for political affairs during the Bush administration, offered words of praise for the former Trump administration’s tough stance on China and lawmakers for bipartisan cooperation on legislation countering China.

And he emphasized his support for the Biden administration’s focus on strengthening unity among allies and partners to confront Beijing on a host of its aggressive actions.

Russia has an interest in seeing a nuclear constrained Beijing, he said, praising strategic working groups such as the Quadrilateral Security Dialogue among the U.S., Japan, India and Australia.

He hailed Biden’s formation of a trilateral security pact among the U.S., United Kingdom and Australia, formally called AUKUS, as potentially “transformational” and welcomed in the IndoPacific.

The deal, announced in September, briefly ruptured relations with France, which saw a lucrative submarine deal with Australia cancelled in favor of Canberra’s new alliance with Washington.

Burns said that more energy needs to be spent in uniting European Union countries to recognizing the threats posed by China, in particular Beijing halting trade with Lithuania over Vilnius’s supportive posture towards Taiwan.

“The Chinese government has launched an intensive intimidation campaign, economic intimidation of Lithuania and the Lithuanians have stood up, and they’ve held their ground and they deserve our support,” Burns said.

China considers the island territory as part of China, while the Taipei government refers to itself as the only legitimate government of the Chinese people.

Burns put his support behind the U.S.’s “One China policy,” which recognizes Taiwan as inseparable from the government in Beijing, but is committed to the self-defense of the island in efforts to promote peaceful dialogue between Beijing and Taipei.

Burns also said it is important for the U.S. to keep a military presence in the Indo-Pacific to deter China from invading Taiwan, in particular among increased rhetoric from the Chinese Communist Party to take over the island and provocations by flying its warplanes close to Taiwan’s airspace.

“The rhetoric of its [Beijing’s] leader and many other Chinese leaders in recent months has been that they intend to take back Taiwan. Our responsibility is to make Taiwan a tough nut to crack.”

Burns is likely to garner a bipartisan vote on his confirmation, receiving praise from Senate Republicans during his hearing.

“It’s appropriate that Ambassador Burns was appointed to this position that really demands a bipartisan approach,” Sen. Jim Risch (R-Idaho), the ranking member of the committee, said in his opening statement