U.S. Treasury Secretary Janet Yellen opens two days of meetings with Chinese Vice Premier He Lifeng on Thursday in a bid to limit the economic fallout from a tense relationship by keeping open the lines of communications on topics from national security to climate change. U.S. Treasury officials have sought to downplay expectations for any breakthroughs from the meetings in San Francisco, where the U.S. President Joe Biden next week will host a summit of Asia Pacific Econoimc Cooperation country leaders, including Chinese President Xi Jinping. Biden and Xi are expected to steal APEC's spotlight with a planned meeting on the summit sidelines.