Those around the world who are looking to the United States for support against intimidation, oppression or outright massacres have learned a tough lesson in the past few years: This U.S. president, despite his bold pronouncements and moral posturing, cannot be counted on.

In Syria, President Obama declared that the brutal dictator Bashar al-Assad “must go.” The U.S. ambassador in that country and other administration officials openly encouraged opposition groups campaigning against the Assad regime. Yet when it came time to organize and provide lethal assistance to moderate opposition groups to help defend them against Assad’s attacks, the president turned away.

According to some news reports, a trickle of weapons and training found its way to the Syrian opposition, but to no discernible effect. In the absence of a U.S.-led effort to empower moderates, other regional powers began to fund extremists. Now, responding to the slaughter on the ground and congressional initiative, the administration has endorsed more overt assistance, but with no useful details and no sense of urgency. It appears it could be way too little and way too late.

Last year, when we learned that Assad had used chemical weapons on his own people and in defiance of Obama’s own red line, the president asked Congress for the authorization to use military force against Syria. I worked with my colleagues to move that authorization out of the Foreign Relations Committee to the floor of the Senate. But when faced with the difficult challenge of persuading the rest of Congress to support his policy, Obama reversed course and said he no longer wanted the authority. Instead, the president jumped in the lap of Russian President Vladimir Putin, who offered a way for Assad to survive, even thrive, while turning over Syria’s declared stockpile of chemical weapons to the United Nations.

Today, after three years of bold rhetoric divorced from reality, 170,000 Syrians are dead, and we are not innocent bystanders. The president encouraged the opposition to swallow deadly risks, then left them mostly hanging. Extremist groups from Syria have surged into Iraq, seizing key territory and resources, and are threatening to completely undo the progress of years of U.S. sacrifice.

The story in Libya is arguably worse for this president’s credibility. Four years after Obama deployed dubious constitutional arguments to send our military forces into harm’s way to bring down the Gaddafi regime, we have now withdrawn our diplomatic personnel from Libya. Once touted by the administration as a new model for cost-effective nation-building, Libya is, according to the State Department, an official terrorist safe haven , and four Americans gave their lives in a brave but tragically under- resourced attempt to mediate tribal disputes.

As in Syria, the entirely predictable consequence of the president’s actions, or lack thereof, has spurred violent chaos and destroyed what was left of Libya’s social order. Now, as the president walks away, his State Department issues the emptiest of statements: “We will continue to engage all Libyans and the international community to seek a peaceful resolution to the current conflict.” Is there a single Libyan who will take solace in those words?

The president’s empty promises and unreliability are at their most acute in Eastern Europe. Our tepid response to Russian aggression in Ukraine for nearly five months emboldened Putin, directly undermining U.S. interests and making Europe, and thus the United States, less secure.

To date, the president has issued plenty of tough statements. He has described Russia as a regional power, labeled Putin as one of history’s losers, called for tough sanctions, explicitly endorsed Ukraine’s attempts to join with the West economically and promised assistance, including military aid, to Kiev.

And while we are seeing the president take some steps in the right direction, which we strongly applaud, U.S. sanctions against Russia and support for Ukraine have been implemented in a day-late-dollar-short method. The military aid for Ukraine that has been delivered consists of little more than body armor and ready-to-eat meals. Meanwhile, Putin openly mocks Obama’s efforts. He sends men, materiel and weapons to the “rebel” troops in eastern Ukraine.

The Russian-backed rebels have been using sophisticated weapons to shoot down Ukrainian military helicopters for months, and tanks have been crossing the border from Russia since mid-June. That same month, NATO commander Gen. Philip M. Breedlove confirmed that Russia was training the rebels to operate “vehicle-borne” surface-to-air missiles, the type of weapon used to shoot down Malaysia Airlines Flight 17. Despite these reports, the administration is still wrestling with an internal debate on whether to provide intelligence information to the Ukrainians to help them prevent attacks from rebels within their own country.

Ha d the president imposed the serious costs on Russia that he has talked about since March, it’s more likely Putin would have decided that the benefit of transferring such weapons to the rebels was not worth the cost.

I support the president’s desire to avoid “stupid” wars and to “steadily advance the interests of the American people and our partnership with folks around the world ,” but, time and again, this president proves that he is uncomfortable being commander in chief and implements policies unsteadily and at odds with his stated goals, further undermining our credibility with these very partners. More often than not, the president doesn’t hit singles and doubles; he just balks.

This is an unfortunate learning moment for those counting on support from the United States in the Middle East, in Europe and everywhere else. But under this president, it’s just where we are. It is hard to watch.

Bob Corker is a U.S. senator from Tennessee and the ranking Republican on the Senate Foreign Relations Committee.