BEIJING, July 6 (Reuters) - U.S. Treasury Secretary Janet Yellen is set to start a four-day visit to Beijing from Thursday that is expected to focus on recalibrating ties between the world's two largest economies locked in confrontation.

Both sides have low expectations for the trip, however. While Beijing wants more dialogue to improve economic ties, it has accepted that both sides have placed safeguarding their own national security above economic ties.

Chinese analysts have told state media that Yellen's April speech, which ranked securing the national security interests of the U.S. and its allies as the top plank of America's economic policy with China did not inspire optimism for the visit.

Zhu Feng, a professor of international relations at Nanjing University, told the Global Times newspaper that Yellen's emphasis on national security meant the U.S. was unlikely to stop the "economic and technological suppression" of China.

Yellen will emphasise the need to work with Beijing on climate change, pandemic preparedness and debt distress, a senior U.S. Treasury official said previously.

She will also tell her Chinese counterparts that Washington is not seeking to decouple the two economies, while reserving the right to protect human rights and U.S. national security interests through targeted actions, the official added.

Even though no major breakthroughs are expected, U.S. officials say Yellen will push to open new lines of communication and coordination on economic matters, and stress the consequences of supplying lethal aid to Russia, an assertion China has adamantly rejected.

When Chinese ambassador Xie Feng met Yellen in Washington on Monday, he urged the U.S. to "pay great attention" and move to tackle China's main concerns on the economy and trade.

Trade tariffs imposed by the Trump administration and sanctions against Chinese firms are the country's chief concerns, said Wu Xinbo, an American studies specialist at Fudan University, who is familiar with Beijing's thinking.

Yellen's long-anticipated trip comes weeks after a visit by Secretary of State Antony Blinken, who agreed with Chinese President Xi Jinping that the mutual rivalry should not veer into conflict, amid a freeze in talks between their militaries.

Both visits are seen as critical to improving communication after the U.S. military shot down a Chinese balloon over the United States.

They come ahead of a possible meeting between President Joe Biden and Xi at the Asia-Pacific Economic Cooperation gathering scheduled for November in San Francisco. (Reporting by Yew Lun Tian and Andrea Shalal; Editing by Clarence Fernandez)