WASHINGTON/BEIJING, Nov 16 (Reuters) - U.S. President Joe Biden pressed his Chinese counterpart on human rights in a video call lasting more than three hours, while Xi Jinping warned that China would respond to provocations on Taiwan, according to official accounts of the exchange. The closely scrutinized conversation between the leaders of the world"s biggest economies was described by both sides as frank and direct as the two sides tried to lower the temperature and avoid conflict. The talks, which began on Monday evening in Washington - Tuesday morning in Beijing - appeared to yield no immediate outcomes, but gave the two leaders opportunity to nudge their relations away from icy confrontation, even as they stuck to entrenched positions. They discussed North Korea, Afghanistan, Iran, global energy markets, trade and competition, climate, military issues, the pandemic and other areas where they frequently disagree. Xi, who has not left his country since COVID-19 spread worldwide from the central Chinese city of Wuhan nearly two years ago, compared the two countries to "two giant ships sailing in the sea" that needed to be steadied so they didn"t collide, Chinese state media reported. "I hope that, Mr. President, you can exercise political leadership to return the United States" China policy to a rational and pragmatic track," Xi told Biden, according to Xinhua, a reference to tough-on-China policies that Beijing hoped would be rolled back after Biden came to office. Biden spoke of avoiding conflict as well. "It seems to me our responsibility as leaders of China and the United States is to ensure that our competition between our countries does not veer into conflict, whether intended or unintended," Biden said during a short exchange observed by reporters at the start of the meeting. "Just simple, straightforward competition." The leaders had a "healthy debate", a senior U.S. official said afterwards. Biden stressed the importance of China fulfilling its commitments under a trade pact negotiated with Biden"s predecessor, Donald Trump, the U.S. official said. China is lagging in a commitment to buy $200 billion more in U.S. goods and services, but Xi told Biden that it was important to avoid politicizing the issue. The two also discussed taking measures to address global energy supplies, U.S. officials said. The contentious issue of whether the United States will send White House envoys to the Beijing Winter Olympics in February did not come up, the U.S. official said. Chinese state media struck an upbeat tone. A screen shows Chinese President Xi Jinping attending a virtual meeting with U.S. President Joe Biden via video link, at a restaurant in Beijing, China November 16, 2021. REUTERS/Tingshu Wang A screen shows Chinese President Xi Jinping attending a virtual meeting with U.S. President Joe Biden via video link, at a restaurant in Beijing, China November 16, 2021. REUTERS/Tingshu Wang "The summit could be taken as a sign that the two economic and political heavyweights could at least avoid a further deterioration in their ties after four years of damage caused by the reckless Trump administration," Wen Sheng, a Global Times editor, wrote in a commentary. RED LINE FOR TAIWAN Sharp differences over the self-ruled island of Taiwan remain. While Biden reiterated long-standing U.S. support for the "One China" policy under which it officially recognises Beijing rather than Taipei, he also said he "strongly opposes unilateral efforts to change the status quo or undermine peace and stability across the Taiwan Strait", the White House said. Xi said those in Taiwan who seek independence, and their supporters in the United States, were "playing with fire", according to Xinhua. "China is patient and seeks peaceful reunification with great sincerity and effort, but if Taiwan secessionists provoke, or even cross the red line, we will have to take decisive measures," he said. A U.S. official said "there was nothing new established in the form of guard rails or any other understandings" on Taiwan, though Biden raised "very clear concerns." China claims the island as its own. Beijing has vowed to bring the island under Chinese control, by force if necessary, and tensions across the Taiwan Strait have escalated in recent months. Beijing objects to Washington"s efforts to carve out more space for Taiwan in the international system, and recent comments by Biden that the United States would defend Taiwan in certain cases also inflamed tensions. Taiwan"s Mainland Affairs Council, responding to Xi"s remarks, denounced China"s "pressure and intimidation", saying the island"s people would not give in to threats. Biden raised other issues that Beijing regards as domestic concerns, including its handling of Tibet, Hong Kong and Xinjiang, where China"s policies face frequent censure by foreign rights groups. Biden and Xi have not had a face-to-face meeting since Biden became president and the last time they spoke was by telephone in September. The U.S. president smiled broadly as the Chinese president appeared on a large screen in the White House conference room. The tone of the meeting lifted investor sentiment, with global stocks hitting new peaks. "At least they are talking," economist Wellian Wiranto of OCBC Bank in Singapore wrote during the talks. "That seems to be the main expectation by global markets when it comes to any concrete outcome – or a lack thereof."