In his speech this week on his plans for the U.S. military presence in Afghanistan, President Trump said he will use the threat of withdrawing foreign aid to put pressure on Pakistan to better support the American mission. Despite proposing dramatic cuts to the State Department and U.S. Agency for International Development budgets, the Trump administration still requested $740 million in foreign aid for Pakistan, so this threat carries significant weight. Then, just one day later, news broke that the State Department is withholding $195 million in military aid for Egypt and has revoked another $95 million in foreign aid, seeming proof that we are willing to use aid as leverage.

But history shows that foreign aid is a poor way to get what we want. Threatening to cut off aid is almost certain to fail in bringing about political change in Egypt, Pakistan or any country that the United States has a strategic interest in supporting.

U.S. foreign aid has long been held out as a carrot to reward countries that embrace democracy and free markets. For example, the Millennium Challenge Corporation, a foreign aid agency created under George W. Bush, awards funds only to countries that are undertaking liberal political and economic reforms. During the Cold War, increased aid was also offered as a potential reward to failing states such as El Salvador. During a visit there by then-Vice President George H.W. Bush at the height of the country’s civil war, El Salvador was promised a massive increase in military assistance in exchange for the removal of military leaders suspected of human rights abuses and greater restraint by the government-aligned “death squad terrorists” who had killed thousands. While death squad killings did decline, the lull in violence was short lived. According to Human Rights Watch, there were 1,900 political killings and disappearances in El Salvador only a year after Bush’s visit. Promises of aid didn’t stop the violence, but Congress still approved the Reagan administration’s $61.7 million aid request to resupply the Salvadoran military, which was apparently running out of bullets.

The cutoff of aid has also been used as a stick — either threatened or enforced — to motivate countries to get back on track with U.S. objectives. In 2010, U.S. military aid to several Pakistani military units was cut as punishment for human rights abuses, including at least 300 extrajudicial executions in the Swat Valley. In a war for “hearts and minds,” killing civilians doesn’t help. But the Obama administration undermined the impact of the cuts by simultaneously negotiating a $2 billion counterterrorism package with Pakistan. The following year, the Obama administration suspended 40 percent of the $2 billion package in an attempt to secure greater cooperation from the Pakistani military in fighting against the Taliban — the very same thing Trump threatened.

Why does aid fail to change governments’ behavior? One of the reasons is that we give most of our foreign aid to countries that are strategically important to the United States — nations like Egypt and Pakistan. We need their continued cooperation on a range of issues, and this ultimately limits the amount of pressure we can apply. Sometimes there are developments beyond our control. Restrictions on foreign aid to Indonesia were eased in 2005 after a tsunami devastated parts of the country. Other times, the cuts in aid are too small to matter. In 2015, $5 million in aid was withheld from Mexico after the summary execution of 22 suspected gang members during the country’s ongoing drug war. But that amounted to 15 percent of U.S. support for the Mexican police and military under the Merida Initiative. The Mexican military continues to support local police forces, recently killing 17 in a firefight, which suggests that little has changed in the Mexican government’s strategy.

Often, cutting aid is simply not enough to force change. In Mali, the Obama administration suspended $70 million in bilateral aid — roughly half of U.S. aid to the country — after a 2012 coup. The State Department said aid would resume at normal levels once democratic rule was restored. The coup leader stepped down, but the military remained in power. Presidential elections were held more than a year later, after French military intervention in the country.

Pressuring countries through foreign aid can also drive them away from the United States. This fear was strongest during the Cold War, when the Soviet Union was actively competing for influence in developing countries, but it’s still very real. In the Philippines, President Rodrigo Duterte’s war on drugs has led to thousands of deaths. In response, the U.S. postponed millions of dollars in foreign aid. Duterte also rejected $280 million in aid from the European Union because it was pressuring him to improve human rights conditions. Aid can no longer buy political influence in the Philippines.

The risk of pushing countries whose cooperation we need closer to Russia, China and Saudi Arabia — all of which have sizable aid programs of their own — is something Congress and the Trump administration should consider. Long-standing relationships, such as we have with Pakistan and Egypt, do need to be revisited. There’s no question that foreign aid needs to be reformed so that it better serves our national interest instead of supporting countries that undermine our goals. But empty threats put us in a poor negotiating position — something that this president should, at least in theory, know a bit about.