At the G-20 summit this week, Chinese President Xi Jinping may pressure U.S. President Donald Trump to halt a planned U.S. arms deal with Taiwan. Xi may even offer a tantalizing (but unreliable) concession on the trade dispute in return for concessions on Taiwan. Accepting such an offer would undermine U.S. national security and the democratic principles Americans support.

Bullies tend to start fights they think they can win, an important consideration when it comes to deterring Beijing from aggression against Taiwan. Unfortunately, due to China’s massive military mobilization and Washington’s past reluctance to provide sufficient arms to Taiwan, the military balance of power in the Taiwan Strait has shifted in Beijing’s direction — making war there more likely. To begin reducing this risk, Washington would be wise to follow through on delivery of the pending arms package for Taiwan.

Based on the hope that economic liberalization would lead to political liberalization, Washington facilitated Beijing’s integration into the global economy. American support for China’s entry into the World Trade Organization epitomized this strategy. Unfortunately, increased wealth did not launch an inexorable march toward freedom in China. Instead, the Chinese Communist Party, or CCP, used its financial windfall to fund a major military expansion, bully its neighbors and attempt to push the U.S. out of the region.

These dynamics have been perhaps most pronounced in the Taiwan Strait.

Taiwan is prosperous and democratic, which creates an uncomfortable contrast for the CCP and an object of emulation for its subjects on the mainland. As in Hong Kong, the people of Taiwan have grown accustomed to their freedoms and are reluctant to give them up.

Impatient — and determined to exert control over the island — Beijing has employed political and military means to isolate and intimidate Taiwan. First, Beijing has pressed countries to cut ties with Taiwan. In 2018 alone, China successfully pressured three more countries to sever Taiwanese relations, leaving only 17 that recognize the island’s government. Taiwan’s diplomatic isolation makes American support all the more important.

More dangerously, due primarily to its extraordinary military buildup, Beijing is moving ever closer to an ability to successfully invade the island.

The U.S. Defense Department’s Indo-Pacific Strategy Report released this month notes that “China has never renounced the use of military force against Taiwan, and continues to develop and deploy advanced military capabilities needed for a potential military campaign.”

Indeed, as demonstrated by an increased number of military exercises near Taiwan, the report warns that the People’s Liberation Army is “preparing for a contingency to unify Taiwan with the mainland by force.”

In the past, Taiwan’s superior technology and geography gave Taiwan a military edge when it came to a potential conflict in the strait. However, as the Pentagon noted, due to China’s military buildup, those advantages are now largely gone.

In fact, as the Defense Intelligence Agency’s 2019 report on Chinese military power assessed, “Beijing’s longstanding interest to eventually compel Taiwan’s reunification with the mainland and deter any attempt by Taiwan to declare independence has served as the primary driver for China’s military modernization.”

Simultaneously, based on an overzealous and counterproductive desire in previous administrations to avoid offending Beijing, Washington has often been reluctant to provide Taiwan the arms it needed. Fearful to not provoke the Chinese, the Obama administration rejected Taiwanese requests for 66 new F-16 fighter jets — instead only offering modifications for its aging aircraft.

Admittedly, America’s arms sales to Taiwan are relatively modest compared to China’s military buildup. However, the failure to provide Taiwan the required weapons exacerbated the shift toward Beijing in the military balance. As a result, across most combat domains, Beijing has established both a quantitative and qualitative advantage over Taiwan.

Consequently, there is a risk that Beijing planners and decision-makers might determine they could launch a successful offensive against Taiwan. That perception in Beijing makes aggression in the strait and a war with the United States more likely.

The bipartisan National Defense Strategy Commission listed aggression against Taiwan as a top concern, arguing that allowing China to absorb Taiwan by military force would constitute a “crushing blow to America’s credibility and regional position.”

In addition to genuine hard-power concerns, there is also a matter of principle. When an authoritarian power threatens and bullies a democratic people, America is not neutral.

Furthermore, providing Taiwan the means to defend itself is not just consistent with sound policy and good principle — it is the law. The Taiwan Relations Act made clear that the establishment of diplomatic relations with Beijing rested on the expectation that the future of Taiwan would be “determined by peaceful means.” To make this a reality, the law says the U.S. will provide the weapons “necessary to enable Taiwan to maintain a sufficient self-defense capability.”

Admittedly, successive U.S. administrations have interpreted and implemented this rather vague statute differently. However, what seems clear is that Taiwan’s ability to defend itself against an increasingly belligerent and capable military threat from the mainland is in doubt. That would suggest that the current arms package under consideration is not only permissible and advisable under the law, but essential.

The administration deserves credit for expanding freedom of navigation operations in the Taiwan Strait and, at least initially, asking Congress to support new arms sales to Taiwan. Those are good first steps, but they are not enough. In addition to providing these arms without delay and stopping the erosion of U.S. military superiority vis-a-vis China, Washington should also provide Taiwan the fighter aircraft and other weapons it needs to make Beijing think twice before undertaking aggression in the strait.

In its report this month, the Pentagon reiterated the U.S. commitment to Taiwan’s self-defense, invoking the words of the Taiwan Relations Act.

Those are good words. But in any potential conversation with President Xi this week, President Trump would do well to remember that it will take more than words to deter aggression from the bullies in Beijing.

Bradley Bowman is senior director for the Center on Military and Political Power at the Foundation for Defense of Democracies, where Mikhael Smits is a research analyst.