A long-awaited summit between US President Donald Trump and Chinese President Xi Jinping is set to take place in Beijing May 14 and 15, with both sides preparing to address a crowded agenda spanning Iranian oil, Taiwan, trade, human rights and technology controls.

Beyond the main geopolitical disputes, the talks are also expected to cover the possible release of Hong Kong media tycoon Jimmy Lai and Beijing's move to discourage local firms from buying Nvidia's H200 artificial intelligence chips, even after Trump approved their export to China.

The summit was originally scheduled for late March or early April, but the White House postponed it because Trump needed more time to focus on the war in Iran. On top of the Trump-Xi meeting's agenda, the ongoing conflict in Iran remains the biggest issue hanging over the talks.

"Iran is the world's largest state sponsor of terrorism, and anyone who's buying oil from Iran is contributing to that," US Trade Representative Jamieson Greer said in an interview with Bloomberg TV on Wednesday. "So when the Treasury takes a step similar to steps it's taken many times over decades with respect to oil refiners who are dealing with Iran, and you have a country that refuses to comply or directs non-compliance, that's going to have to be a discussion item."  

Greer said the issue had already been raised at the staff level between China and the United States. But he also made clear that Washington did not want the Iranian oil dispute to dominate the summit or derail any wider understanding reached in Beijing.

"We're looking for stability with China," he said. "We don't want this to be something that derails the broader relationship, or any agreements that might come out of our meeting in Beijing."

He said countries sometimes adopt domestic laws and regulations that conflict with US policy, adding that the European Union has, for years, maintained a blocking statute preventing compliance with US sanctions on Cuba. He said Washington would expect "some kind of resolution" when Chinese rules clash with US sanctions.

"What China is doing is serious. We take it very seriously. But again, for us, it's not something where we're going to let that become the only thing we talk about in the relationship," he said. "We'll address other issues related to trade and geopolitics and foreign policy and everything that comes with the relationship between two of the most important countries in the world."