U.S. Treasury Secretary Jack Lew wrapped up a two-day visit to China on Wednesday having reopened dialogue on pressing issues of economic reform but saying more action is needed on China’s exchange rate.

Lew, in his first international trip since taking office last month, also raised concerns about security issues involving cyber threats and North Korea.

His talks with China’s new leaders and senior economic officials as well as with U.S. business leaders in the country were aimed at improving cooperation between the two economic powerhouses and boosting economic growth.

U.S. lawmakers are particularly concerned about the value of the Chinese yuan, which they claim is undervalued and hurts American manufacturers.

The currency hit an all-time high against the dollar on Wednesday, but Lew said China needs to make more progress reforming its foreign exchange regime.

“China’s exchange rate should be market determined. That’s in our interest and China’s interest. They recognize the need to do it for internal reasons as well,” Lew told reporters shortly before heading back to Washington.

As for other economic reforms, he said that talks showed China “has made a serious commitment.”

“The challenge will be to drive forward toward material progress,” he added. “The dominant economic theme was what can be done to generate more domestic demand and more growth.”

During his talks, Lew also raised the issue of computer hacking, a top concern for national security and economic stability. U.S. President Barack Obama last week convened a meeting with CEOs at the White House on such digital attacks and later called Chinese President Xi Jinping over the issue.

“It has to be recognized, as the president indicated, this is a very serious threat to our economic interests. There was no mistaking how seriously we take this issue,” Lew said.

Other potential destabilizing threats include China’s neighbor North Korea, and Lew said that China and the United States will continue to be engaged together.

“We made clear that the U.S. views the provocative actions of North Korea as very serious and we will continue to pursue methods available to change the policy perspective in Pyongyang. We share a common objective of a denuclearized Korean peninsula and we will continue to discuss it,” he said.

(Reuters)