American flags have been blanketing the streets of Hong Kong following President Trump’s bold decision to sign the Hong Kong Human Rights and Democracy Act into law. It was not just the right thing to do — it’s also a crucial move in ongoing trade negotiations.

For the past several months, Hong Kong has treated the world to the noble spectacle of brave citizens fighting to defend their freedom. Mass demonstrations, peaceful protest, and democratic engagement have sent a clear message to a Chinese government eager to infringe upon Hong Kong’s territorial integrity and lawful rights.

Recent elections have illustrated how united Hong Kongers are standing up against an encroaching Communist Party. Pro-democracy candidates scored a landslide victory, propelling the grassroots protests into a position of unprecedented political power.

President Trump knows that Hong Kong needs the backing of the United States in order to maintain its independence. But he also knows that standing with Hong Kong is another lever to pull in his negotiations with Xi Jinping and the Chinese Communist Party.

By offering Hong Kong official tools of support, President Trump has broadened the trade dispute in accordance with American interests, while also paving the way towards a peaceful resolution of China-Hong Kong tensions.

Using diplomacy to achieve peace and prosperity has been a hallmark of President Trump’s foreign policy agenda. Trade negotiations with China are a case in point. President Trump wants to rebalance our trading relationship with China in order to ensure peace for generations. That means putting our relationship on a new foundation capable of supporting a long and prosperous friendship.

Similarly, Hong Kong and China need to reconfigure their relationship in order to secure future peace and prosperity for both peoples. Chinese attempts to strong arm Hong Kongers into submission will end in catastrophe, and American backing of Hong Kong is necessary if the island and mainland are ever to enjoy a relationship built on mutual respect and advantage.

President Trump knows that continuing to export the livelihoods of millions of Americans to China is neither desirable nor tenable. We need a mutually beneficial relationship with China that brings opportunity back to the American heartland. With a new deal that addresses structural challenges the Chinese economy poses to American workers, President Trump hopes to do just that, and pressuring the Chinese government with Hong Kong only makes that task easier.

Throughout negotiations, the Chinese have been reluctant to get a deal over the line, walking away from agreed upon terms several times. By supporting Hong Kong, President Trump is showing the Chinese Communist Party that he will not sit idly by while they jerk trade negotiations around.

Kimberly Guilfoyle (@KimGuilfoyle) is a senior adviser to Donald J. Trump for President, Inc.