US President Barack Obama feels that dinners with President Xi Jinping in recent years have been the most constructive engagement between the two leaders, according to a senior Obama adviser.

Ben Rhodes, Obama's deputy national security adviser for strategic communications, said the US president has developed a good relationship with President Xi. "That doesn't mean we agree with everything Xi does, but I think they have been able to have constructive conversations," Rhodes said on Tuesday afternoon during a conference call on Xi's state visit.

Rhodes, who has attended many meetings between the two leaders, described formal meetings as sitting down, going through a long list of agenda items and stating each other's position on issue after issue.

He said such bilateral meetings are "necessary and very important", but added that "what has been distinct about their relationship since Sunnylands (California) is, far and away, the constructive engagement they had in their private dinners".

"Both in Sunnylands and in China, President Obama commented afterward that he felt the most constructive engagements were when they were able to talk for several hours over dinner without a formal agenda and give a vision for where they want to take their country, give a vision for how they think the US and China should operate together in the world, and kind of put aside the talking points and actually get a window into one another's world view - and those world views are very different," Rhodes said.

"And that's part of why I think the conversations are useful and important, because it provides the context for all of these issues."

Xi and Obamamet in June 2013 for a shirt-sleeve summit in the California desert retreat of Sunny-lands, and they met again in November last year in Beijing for a private dinner in Yingtai, an imperial palace on an island within Zhongnanhai, the central government's headquarters.

Rhodes said such dinners give them the ability to step back and offer a perspective of where they are in terms of their relationship. While President Obama was able to hear from President Xi about his domestic programs, Obama was also able to share some of his thoughts on domestic programs.

"It doesn't mean they are in perfect agreement. But they have the understanding as to where they come from on these issues," Rhodes said. He described last November's breakthrough on climate change as a result of the informal talk between the two leaders in Sunnylands, and he credited the expanded military-to-military exchanges between the two countries to a dinner engagement.

Rhodes said that starting President Xi's state visit this week with a dinner is very important because there won't be a long formal agenda to go through. "They can step back and look at the strategic context, acknowledge the differences and some tensions that are there, but also look for opportunities for the next phase where we can cooperate.