Swelling crowds of pro-democracy demonstrators in Hong Kong on Monday plunged Asia’s normally staid financial hub into a tense standoff with Beijing that strikes directly at China’s expanding political grip in the former British colony.

The rapidly escalating protests are aimed at forcing Beijing’s Communist leaders to abandon newly declared powers to weed out any candidates in upcoming Hong Kong elections. Yet many on the streets proclaimed they are fighting for something even bigger: preserving a vision of Hong Kong promised 17 years ago when it reverted to Chinese rule.

At the time, Chinese leaders promised a state within a state, saying they would allow special hands-off provisions for Hong Kong such as elections and a degree of self-rule in policymaking. But protesters accuse China of reneging on the deal and trying to exert its control over every aspect of Hong Kong’s political affairs.

The mounting protests present a conundrum for Beijing.

Too hard a crackdown could drive more people to the pro-

democracy cause, which would embarrass Chinese authorities, who would never permit such a challenge on the mainland. Yet, by the same token, allowing the protesters some room risks encouraging others to question Communist control in the rest of the country over such issues as media freedom, economic development and minority rights.

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“Resign!’’ some protesters cried in jeers directed at Hong Kong’s leaders, whom they perceive as unwilling to stand up to Beijing.

Even the choice of locations for the protest rallies appeared to be a direct poke at authorities who prize Hong Kong’s reputation as a place for easy commerce. Thousands of demonstrators turned multi-lane highways into protest plazas and adopted the “occupy” theme of sit-ins against Wall Street.

By sundown Monday, police had bolstered their ranks around blockades and cordons at some government buildings but did not renew attempts to confront or disperse the crowds.

Both sides seemed to be readying for a drawn-out duel.

Protesters — led by university students and teenagers barely old enough to remember when the Union Jack flew over Hong Kong — believe they are fighting for nothing less than the future of Hong Kong as they know it.

Chinese leaders, however, are unlikely to display any sign of weakness and reverse rules laid down last month that give Communist leaders the power to weed out candidates not loyal to the party.

In a sign of digging in, Chinese state-run media, including the People’s Daily, linked the protesters to “foreign anti-China forces’’ with alleged ties to the West. The state-backed Global Times newspaper further claimed that U.S. media outlets were trying to “stir up Hong Kong society” by drawing parallels with the 1989 Tiananmen Square demonstrations that were crushed by Chinese authorities.

Authorities in Hong Kong cracked down on pro-democracy demonstrators on Sunday using tear gas and pepper spray. Thousands of demonstrators turned out on the downtown streets again on Monday to support the protest. (The Washington Post)

At the White House, press secretary Josh Earnest urged restraint on the part of authorities.

“We believe that an open society with the highest possible degree of autonomy and governed by the rule of law is essential for Hong Kong’s stability and prosperity,” he said. “Indeed, this is what has made Hong Kong such a successful and truly global city to this point. We have consistently made our position known to Beijing and will continue to do so.”

But protesters were drawing comparisons between what they see as their peaceful approach and the response of authorities.

“People use peace and hope, while the government used tear gas and pepper spray,” said a protest leader, Benny Tai, at a rally in Hong Kong’s upscale Causeway Bay section, according to the South China Morning Post.

A failed attempt by police Sunday night to intimidate the protesters — using force, tear gas and pepper spray — appeared to backfire and brought more people to the opposition ranks. Police said clashes during the previous three days had injured nearly 30 people and 12 police officers.

In an apparent reevaluation of the hard-line approach, authorities on Monday announced the withdrawal of some riot police, even as they defended their use of tear gas a day earlier.

The step back brought almost a festive air to the crowds, which remained on the streets as dawn neared Tuesday. People broke into song throughout the night, shared meals passed out by volunteers and waved illuminated cellphones en masse.

Some held up umbrellas — which have become a symbol of the protests as they were used to shield against pepper spray and provide shade against the sweltering heat.

The coming days could be pivotal for both sides.

If the protests continue through Wednesday — the beginning of a two-day holiday in Hong Kong — many believe they could draw even larger crowds.

In a preemptive move, Hong Kong’s leaders announced they were canceling fireworks planned to celebrate Wednesday’s China National Day. Many schools and colleges would remain closed Tuesday, officials announced.

Beijing, meanwhile, has few immediate solutions.

“The government has to be careful not to alienate the public,” said Michael Davis, a law professor at the University of Hong Kong. “As we saw yesterday, every time the government takes hard action, people come running to join the protest.”

Yet China’s leaders are notoriously reluctant to negotiate — much less reverse themselves — partly for fear it could inspire more mutinies against central rule.

Chinese authorities, for example, took quick steps after Sunday to tighten social media and some online reports of the protests. In an apparent bid to stop images circulating of the Hong Kong dissenters, Beijing’s leaders blocked the photo-sharing app Instagram. Internet images pose a greater challenge to Beijing’s censors because they cannot scan for keywords as they can with written posts, which are closely monitored.

Some experts pointed out that the Communist Party keeps a garrison of People’s Liberation Army soldiers in Hong Kong.

“Deploying the PLA would certainly scare everyone off the street immediately,” said Willy Lam, an analyst at the Chinese University of Hong Kong. “But it would also make the front pages of every paper in the world. For them, I think it remains something of a last resort.”

In an apparent reaction to Chinese accusations of a foreign hand in the protests, the U.S. Consulate stressed in a statement that Washington does “not take sides in the discussion of Hong Kong’s political development, nor do we support any particular individuals or groups involved in it.”

In response, a spokeswoman for the Chinese Ministry of Foreign Affairs, Hua Chunying, warned against foreign interference, saying in a statement that “Hong Kong is China’s Hong Kong.”

CORRECTION: An earlier version of this article misstated the number of years since Hong Hong Kong reverted to Chinese rule. This version has been corrected.

Murphy reported from Washington. Liu Liu in Beijing contributed to this report.