In August 2001, on his first overseas trip as chairman of the US Senate Foreign Affairs Commission, Joe Biden went to Beihai Ha, China.

Biden's goal in attending a series of meetings with the Chinese leadership at the time was to help usher in a pivotal era in bilateral relations, including forging a trade connection that allowed Beijing to join the Trade Organization.

"The US welcomes the rise of a prosperous and integrated China in the international arena, because we expect the country to abide by the rules," Biden told Jiang Zemin, then president of China.

A few days later, Biden arrived at Yanzikou, a village near the Great Wall in Beijing, enthusiastically interacting with locals who were amazed at his arrival.

"Washington welcomes Beijing's rise as a great power, because great powers will respect international rules in areas such as nonproliferation, human rights and trade," Biden said.

Nearly two decades after Biden's visit, China has emerged as a powerhouse.

As relations between Washington and Beijing reached their lowest level in decades, and the "pro-China" accusations President Donald Trump had against Biden, the Democratic presidential candidate's tone changed drastically.

"America needs to be tough on China," Biden wrote in an editorial in Foreign Affairs.

Biden said he had a "long-standing interest" in China's change process 40 years ago, after his first visit to the country in April 1979 when "was just entering the Senate".

Welcoming Chinese officials as US vice president in May 2011, Biden reminisces about that trip with respect.

After his visit in 1979, Biden still regularly criticizes China, in the context of its growing rapidly.

By the late 1990s, however, Republicans and a growing number of moderate Democrats praised the benefits of a more free trade state with China.

Like many other congressmen, Biden said that China's global integration could "affect the structure of the internal economic, social and political system" of this country.

Biden also predicts that the chemical and livestock industries in his hometown of Delaware will benefit, along with General Motors and Chrysler, two corporations that operate large factories in the state.

Trump now calls China's accession to the WTO "one of the greatest geopolitical and economic catastrophes in world history".

After decades, the transformation across the economic, political and social aspects in China did not go as expected of Biden.

Some Democrats blame former President George W. Bush for neglecting China at the critical juncture.

Many American companies and consumers benefit from China's commercial integration.

According to one study, between 1999 and 2011, competition from China cost the US more than two million factory jobs.

Towards the end of his first term, Barack Obama took an ambitious turn in US foreign policy of pivoting the Middle East to Asia, mainly in response to challenges from China.

Kurt Campbell, the US assistant secretary of state for East Asia and Pacific affairs at the time, said Biden ultimately rated Xi as a tough man, doubting American power and believing in the Chinese political system.

Before Washington's pivot strategy, Beijing began to push territorial claims in the South China Sea and East China Sea, where the US military is present.

"I want to make it clear that if China adheres to basic international rules, we will have no problem. However, to the extent that they seek to fundamentally change the principles that constitute freedom of goods.

Last month, hours before Biden addressed the Democratic presidential nomination in Wilmington, Delaware, 75 Republican security experts, some of whom had previously worked for Trump, declared in favor

They rated Trump "lacking the character and capacity to lead the country", referring to the president's close relationship with Xi, whom Trump once hailed as "an excellent leader".

This statement is in line with Biden's view that Trump's tough on China is not true.

Biden's strategy seems to stem from political pressure to be tough on China.

Biden's all-encompassing policies at times become ambiguous, however.

While Trump has called for sanctions on China, Biden aides have insisted on restoring America's domestic strength.

In addition to confrontation, Biden also intends to try to cooperate with China on a number of issues such as climate change, health security, Iran and North Korea, but may be hindered by the hawk officials.

Susan Shirk, a China scholar at the University of California, USA, said that Biden's team will use the "stick and carrot" strategy to "punch and rub" in future negotiations with the North.

However, analysts are of the opinion that if Biden was elected, his 40-year relationship with China would fall under unprecedented tension, with larger conflicts seemingly inevitable, amid mastery.