China’s leader, Xi Jinping, has in recent weeks made deals and pledges that he hopes will position his country as an indispensable global leader, even after its handling of the coronavirus and increased belligerence at home and abroad have damaged its international standing.

In doing so, he has underlined how difficult it will be for President-elect Joseph R. Biden Jr. to forge a united front with allies against China’s authoritarian policies and trade practices, a central focus of the new administration’s plan to compete with Beijing and check its rising power. The image of Mr. Xi joining Chancellor Angela Merkel of Germany, President Emmanuel Macron of France and other European leaders in a conference call on Wednesday to seal the deal with the European Union also amounted to a stinging rebuke of the Trump administration’s efforts to isolate China’s Communist Party state.

The deals show the leverage Mr. Xi has because of the strength of the Chinese economy, which is now the fastest-growing among major nations as the world continues to struggle with the pandemic.