The U.S.- China relationship should play a "primary role" in the broader U.S. foreign affairs strategy, while enhancing mutual understanding and trust is critical to an across-the-board collaboration between the two countries, former U.S. National Security Advisor Brent Scowcroft said on Wednesday.

China and the United States are influencing the world everywhere. China is a "rapidly growing power with growing interests around the world, and we need to work together," Scowcroft told Xinhua on the sidelines of a seminar hosted by the Woodrow Wilson Center, a Washington-based think tank.

Scowcroft was "very optimistic" about the upcoming summit between Chinese President Xi Jinping and his U.S. counterpart Barack Obama, saying one of the first things both countries need to do is to understand each other better.

"We have very different histories, cultures and so on. I think the opportunity for the two leaders to sit down and talk is extremely important," he stressed.

"I don't think we have those fundamental disagreements," said the former national security advisor to former U.S. Presidents Gerald Ford and George H. W. Bush, adding that "but we don't understand each other well enough."

There are no areas China and the United States could not discuss to deepen their collaboration, as both countries have "worldwide" interests, he said.

Understanding each other is one of the best starts to better cooperation in resolving global challenges, he said.

Xi and Obama will meet on June 7-8 in California.