BEIJING — China’s central bank moved on Friday to give the country’s slowing economy a jolt, saying it would essentially inject $126 billion into the financial system as Beijing fights an escalating trade war with the United States and contends with a dangerous addiction to debt at home.

The move signaled China’s willingness to ease up on a campaign to curb the borrowing that has weighed on growth in the country’s economy, the world’s second largest, and potentially to open its lending machine up even further if the trade dispute begins to take an even greater toll.

The People’s Bank of China said that it would cut its reserve requirement ratio — the amount of cash from deposits that lenders must keep in their coffers — by 0.5 percentage point on Sept. 16, which would add about 900 billion renminbi to the financial system.

Some banks will see their reserve ratio cut by one percentage point to promote lending to small businesses and private enterprises. Senior officials also indicated this week that they planned to loosen restrictions on local governments related to raising money for infrastructure projects.