China on Tuesday kicked off a summit marking the 10th anniversary of its Belt and Road Initiative -- an ambitious yet controversial undertaking to boost connectivity and trade across the world with Chinese money and know-how in infrastructure development.

World leaders including Russia's Vladimir Putin are gathering in Beijing for the high-profile event, which takes place in the shadow of a spiraling war between Israel and Hamas.

Since its launch by Chinese leader Xi Jinping in 2013, the Belt and Road Initiative (BRI) has poured hundreds of billions of dollars to power the construction of bridges, ports, highways, power plants and telecoms projects across Asia, Latin America, Africa and parts of Europe.

Hailed by Xi as a "project of the century," the BRI has emerged as a glaring symbol of China's rise as a global power. But it has also been viewed with growing skepticism, especially in Western capitals where governments are wary of Beijing's global ambitions.

The massive undertaking has been plagued by criticism. Beijing has been accused of straddling developing countries with crippling debt, while its sprawling projects have often faced concerns -- and even protests -- over their environmental costs, labor violations and corruption scandals.

A decade on, Xi's global building spree is at a crossroads. Chinese investment in BRI projects has tapered off as the world's second-biggest economy slows. Recipient countries are struggling more than ever to repay their debts amid global economic headwinds from the Covid-19 pandemic and the war in Ukraine.

Meanwhile, the United States, which sees the BRI as a a tool for Beijing to extend its global influence at the expense of American power, has proposed its own investment program to boost global infrastructure development.

In the Chinese capital, security has been tightened, with road closures and a heavy police presence as leaders and delegations from around the world arrived.

Here's what you need to know about Xi's signature foreign policy strategy.

What has it achieved?

Originally envisioned as an overland "belt" and a maritime "road" connecting China with Europe and Africa, the BRI has funded infrastructure and energy projects across the developing world.

Bankrolled by China's development banks as well as state-run commercial lenders, Chinese construction firms have paved highways from Papua New Guinea to Kenya, constructed ports from Sri Lanka to West Africa, and provided power and telecoms infrastructure from Latin America to Southeast Asia.

Beijing says more than 150 nations have signed cooperation agreements under the auspices of BRI, with commitments made for more than 3,000 projects and "up to one trillion dollars of investment mobilized."

But tracking BRI financing is notoriously tricky as Beijing doesn't share this data openly and a wide range of financial entities play roles.

According to a study by Boston University's Global Development Policy Center, China's two main development banks provided at least $331 billion to government borrowers in developing countries from 2013 to 2021.

And in the first five years of the initiative, China on average spent more than twice as much financing overseas development projects per year as any other major economy -- including the US, according to AidData, a research lab at William & Mary in the US.

Chinese officials have lauded the initiative for "transcending the old mindset of geopolitical games" and "creating a new paradigm of international cooperation."

What are the risks and criticism?

While the BRI has provided crucial funding to poor countries -- drawing comparison to America's Marshall Plan to rebuild Europe after World War II, critics say its projects have come at a cost.

Some have been accused of lax environmental and labor standards, others have being repeatedly stalled by funding shortfalls or political pushback.

Chinese-built fossil-fuel power plants emit around 245 million tons of carbon dioxide per year, according to the Global Development Policy Center, which also found Chinese development finance projects have significantly higher risks to biodiversity and to Indigenous lands than projects financed by the World Bank.

But the top concern is risky lending, with critics accusing China of saddling low- and middle-income governments with overly high levels of debt relative to their GDPs.

Accusations that Belt and Road is a broad "debt trap" designed to take control of local infrastructure, while largely dismissed by economists, have sullied the initiative's reputation -- especially after Sri Lanka ceded control over the port of Hambantota to China after failing to repay its debt.

More recently, China's overseas lending portfolio has shifted to supporting borrowing countries in distress, researchers say, amid a changing financial climate and challenges for countries repaying hefty loans to Beijing and other lenders.

What comes next?

When it was first proposed, the BRI was partially designed as a way to channel China's excess capacity overseas and open new markets for Chinese goods.

But as the Chinese economy slows, the ambitious program appears to be loosing steam -- a slowdown that started even before the Covid pandemic hit.

Overseas financing from China's two development banks to government borrowers dropped considerably from a peak in 2016 of $87 billion to $3.7 billion in 2021 -- though this doesn't include funds from other lenders like commercial banks or other entities, according to the Global Development Policy Center data.

China will be navigating the second decade of the Belt and Road amid stark economic challenges at home. An expected post-Covid economic rebound has not materialized and local governments are grappling with mounting debt linked to a property crisis.

It remains to be seen to what extent Beijing's domestic economic challenges will impact its overseas lending in the longer term, but there are signs of shifting strategies now.

Analysts have noted a move away from a focus on grandiose -- but often wasteful -- multi-billion infrastructure projects to smaller ones with better returns, such as those involving renewable energy and digital technology.

China may also look to place more emphasis on environmental issues, better social protections and due diligence -- especially as Beijing and its banks learn lessons from the project's first decade, analysts say.

In 2021, Xi called for the prioritization of "small and beautiful" projects, which Chinese officials suggest will appeal to local populations. Later that year, Xi pledged that China would not build any new coal-fired power projects abroad.

The BRI has also spurred other countries to increase their own efforts toward supporting infrastructure projects in the developing world.

In June 2022, leaders from the Group of Seven advanced economies promised to unleash $600 billion in investment by 2027 to "deliver game-changing projects to close the infrastructure gap" between countries.

Last month, the US, Saudi Arabia, the United Arab Emirates, France, Germany, Italy and the European Union announced their own plan to link Europe, the Middle East and Asia by rail.