"I believe we must seek to engage and collaborate with China where possible, but also be prepared to confront inappropriate behaviour if China chooses to act contrary to our interests," Mattis told members of the Senate Armed Services Committee in a written submission of answers ahead of his confirmation hearing.
"China's behaviour has led countries in the region to look for stronger US leadership," he said adding that if confirmed, he will examine ways to strengthen US allies and partners, while taking a careful look at its own military capabilities in the region.
Mattis said upholding freedom of navigation and overflight worldwide are important US interests, and vital to the defence of its other national security interests.
"If confirmed, I will support policy measures designed to preserve and protect the continued global mobility of US forces," he said.
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Responding to a question, the retired marine general said as one of the world's busiest trade corridors, the Indian Ocean is important to Asia's economic growth and global trade.
"We have a strong interest in ensuring safe and secure access to maritime routes there, and to a stable, peaceful, and prosperous region," he added.
Mattis said the US should maintain a military posture in the region that is capable of persistent engagement with all countries in the Asia-Pacific.
"If confirmed, I will examine the progress of the laydown plan, which I understand is part of a long-standing agreement with Japan, and advise the Committee of my assessment," he said.
Mattis said the US must cooperate closely with its allies in the region, in particular South Korea and Japan, and work with other states with important interests in the situation, including Russia and China.
"We need to continue to strengthen our homeland and theatre missile defence capabilities while working with our allies to strengthen their military capacity to deter and, if necessary, respond to aggression by North Korea," he said.
He told lawmakers that the security situation on the Korean peninsula remains volatile due to continued provocative statements and actions by the North Korean leadership.
"These include the expansion of its nuclear weapons programme, continued development of increasingly sophisticated ballistic missile capabilities, and repeated threats to the US and its allies in the region," he said.