BEIJING—Chinese President Xi Jinping signaled a recalibration of his global infrastructure program, pledging to curb corruption and control lending that has drawn criticism from developing economies.

Opening a two-day meeting in Beijing with leaders from some three dozen countries, Mr. Xi said Friday that China would enhance transparency and ensure financial sustainability in his signature Belt and Road Initiative.

The comments mark a softening of the triumphalist tone Mr. Xi’s government has used to promote the program, which has stirred disquiet at home and abroad. Foreign critics have blamed Belt and Road—Mr. Xi’s vision for updating ancient Silk Road trading routes—for heaping onerous debt onto participating countries, while some Chinese say Beijing’s assertive diplomacy has generated international pushback.

“Everything should be done in a transparent way, and we should have a zero tolerance for corruption,” Mr. Xi said. He promised a “debt-sustainability framework” for Belt and Road projects and to encourage compliance with international standards in infrastructure contracting.

Mr. Xi invited foreign and private-sector partners to contribute more funding, a contrast to his pledges of Chinese financing in a similar speech two years ago.