US Defense Secretary Mark Esper said Tuesday he plans to visit China this year for talks on "crisis communications," as Washington takes a tougher stance against Beijing in the disputed South China Sea.

Esper said he has spoken to his Chinese counterpart several times and hopes to make the trip by year's end.

He told a security seminar that one of the goals of the trip would be to "establish the systems necessary for crisis communications and reinforce our intentions to openly compete in the international system in which we all belong."

Secretary of State Mike Pompeo said last week the United States would treat Beijing's pursuit of resources in the South China Sea as illegal, ramping up support for Southeast Asian nations with rival claims and triggering a furious response from Beijing.

Secretary of Defense Mark Esper says he plans to visit China for talks on "crisis communications"
Secretary of Defense Mark Esper says he plans to visit China for talks on "crisis communications" POOL / Greg Nash

It was the latest forceful statement by President Donald Trump's administration to challenge China, which he has increasingly cast as an enemy ahead of November elections.

"We are making clear: Beijing's claims to offshore resources across most of the South China Sea are completely unlawful, as is its campaign of bullying to control them," Pompeo said in a statement.

Esper said Tuesday that China "has no right to turn international waters into a zone of exclusion for its own maritime empire."

He added: "We are not in search of conflict. We are committed to a constructive and results oriented relationship with China and, within our defense relationship, to open lines of communication and risk reduction."