The U.S. must continue to work with China on important issues including intellectual property, rare-earths supply, investment treaties and the yuan currency, a senior Treasury official said Friday.

Lael Brainard, Treasury Undersecretary for International Affairs, told the Council on Foreign Relations that the United States had made "material progress" on several important issues in its dealings with China during a visit by Chinese President Hu Jintao to Washington this week.

But there was plenty more to do, she said in response to audience questions, including urging China to further develop its intellectual-property rules.

"The intellectual-property issues with China are large and we will continue to move forward with them," she said, also noting that the United States had obtained a concrete agreement on software use during Hu's visit.

On trade and investment, Brainard said the United States was examining possibilities for new agreements.

"We are engaging China on the possibilities for bilateral-investment treaties even as we are so focused on what the model will be," she said. "There are a lot of differences between the way China approaches investment treaties, traditionally."