TAIPEI, Taiwan — Chinese leaders convening in Beijing on Friday for the most important political conference of the year issued a call to bolster scientific and technological competitiveness, floated changes to Hong Kong's electoral system and announced a pickup in military spending.

One common but unspoken thread? Competition with the United States.

Much as China looms large in Washington, the United States is casting a growing shadow over Chinese policymaking as the world’s second-largest economy embarks this week on what Premier Li Keqiang called “a new journey to build China into a modern socialist country in all respects.”

In an opening speech before the National People’s Congress kicked off Friday, Li unveiled a new national development plan centered on a heightened emphasis on research and innovation. China’s 14th Five-Year Plan, which covers 2021 to 2025 and offers a vision of China further beyond, stresses “self-reliance and self-improvement” in seven cutting-edge fields, including artificial intelligence, semiconductors and biotechnology.

Frictions with the United States coursed below other issues on this year’s agenda. Officials unveiled far-reaching proposals for Hong Kong that would decisively purge members of the opposition pro-democracy camp — many of whom Beijing has slammed as U.S.-backed, “anti-China forces” — from local elections. By placing power to effectively screen candidates for Hong Kong’s legislative council and its chief executive with an expanded, pro-Beijing committee, the new amendments would ring a death knell for representative politics in the city.

The government also released a new budget for 2021 that showed military spending re-accelerating to grow 6.8 percent for the year. That was a slight uptick from last year, when China tightened purse strings to navigate the coronavirus outbreak.

As President Xi Jinping looked on at the Great Hall of the People, Li told nearly 3,000 delegates that China scored a “major strategic success” against the coronavirus, had conquered rural poverty and now looked forward to a “new stage” of its ascent. Chinese research and development spending will rise by 7 percent a year, faster than before, Li pledged, while government funding for basic science research will rise 10 percent.

China would patiently nurture breakthroughs, Li said, “just as a blacksmith in past years would spend years forging the perfect sword.”

China’s R&D spending has steadily ratcheted up from below 1 percent of annual economic output in 2000 to well above 2 percent. But in recent months, Chinese leaders have spoken urgently about the need to invest more at a moment when China is subject to hobbling tech sanctions that deprive it of cutting-edge semiconductors, as well as other forms of competitive pressure from Washington.

“Given the uncertainty of U.S.-China relations and the inability to rely on partnerships with the U.S., so much comes down to domestic innovation,” said Matthew Funaiole, senior fellow at the China Power Project at the Center for Strategic and International Studies in Washington. A prevailing question in China, Funaiole said, is: “How do we reach parity with the U.S., and what happens after that?”

In a January speech transmitting Xi’s thinking to top party officials, Chen Yixin, a senior Xi ally, said that “containment and suppression by the United States is a major threat, both a skirmish and a protracted war.”

But he urged party cadres to be confident. “The trend is ‘the East is rising, and the West is declining,’ and developments in the international situation are favorable to us,” Chen said, according to a transcript of his remarks.

That hard-nosed thinking has similarly taken hold in Washington, where President Biden has promised to pursue “extreme competition,” but not conflict, with China and to pour investment into transformative technologies.

Biden and his senior advisers have also taken a hard line against China’s tightening control over Hong Kong. Beijing has framed the fate of Hong Kong in nationalistic terms, describing it as a tug of war between China and the West, between patriots and subversive, U.S.-backed activists.

One year after the National People’s Congress passed a sweeping national security law that expanded Hong Kong police powers and paved the way for criminal charges against dozens of activists and former politicians, officials said they needed to go further.

Wang Chen, an NPC standing-committee vice chairman, introduced proposals Friday to change the “size, composition and formation” of an election committee that chooses Hong Kong’s chief executive. The committee would play a role in nominating and electing members of Hong Kong’s legislative council, which Wang said would close “clear loopholes and deficiencies” in current elections that allow for the election of “anti-China, destabilizing elements.”

Carl Minzner, a professor at the Fordham School of Law who specializes in Chinese politics and law, said that by screening candidates for office, Chinese authorities are “dismantling the institutions of electoral democracy and installing a version of the stage-managed one you see in mainland China.”

Minzner predicted more measures to follow, including changes to Hong Kong’s courts and an overhaul of the school curriculum. “There will be a continually developing line about the need to get rid of Western influence from Hong Kong,” he said. “This will be a broad, political rectification not just of Hong Kong institutions but of society itself.”

Shortly after Beijing officials announced outlines of the amendment Friday, Carrie Lam, the Hong Kong chief executive, issued a statement that again struck a nationalistic note.

The electoral changes would “ensure patriots administering Hong Kong,” Lam said. “Our Motherland will forever provide staunch support to Hong Kong.”