I recently returned from a gathering of the world’s top security officials in Munich, Germany, deeply concerned about America’s standing in the world.

Last month, I joined more than 50 senators and representatives at the Munich Security Conference. The annual gathering began in 1963, during the height of the Cold War, to bring Americans and their transatlantic allies together to discuss the world’s most pressing security challenges.

It is clear from my discussions in Munich that our allies have serious doubts about American leadership and the current course of U.S. foreign policy. It’s normal for us to at times disagree with our allies — sometimes it can be a useful exercise to reach a better outcome. But I am worried that this administration’s treatment of our allies has further alienated them at a time when we need them most.

As the world evolves, we must make necessary adjustments to our foreign policy to ensure it continues to serve U.S. interests. But the United States cannot tackle — much less resolve — the multitude of global challenges we face on our own. We cannot stop Russian and Chinese aggression, cyber crime, terrorism, drug trafficking, global pandemics, or climate change, to name a few, without partners. The partners we have relied on over the last 70 years are those that share our values — a respect for democracy, human rights, and the rule of law.

Take a look at our approach on Iran. I agree with the administration that the Iranian government is a destabilizing force in the Middle East and a threat to key allies like Israel. It subjects its citizens to terrible human rights violations, flouts international norms, and supports terrorist activity — recently on European soil.

But this administration’s decision to withdraw from the Joint Comprehensive Plan of Action, otherwise known as the Iran nuclear deal, imperfect though it is, has created a rift between the U.S. and our European allies that Iran is masterfully exploiting. Just consider the audible silence that met Vice President Mike Pence in Europe when he publicly lambasted our European partners for remaining in the JCPOA. Instead of working with our allies to find ways to stop destabilizing Iranian activity, the administration is publicly feuding with them.

Part of this erosion in America’s standing is due to our sinking credibility. How can our allies trust in the U.S. when the president announces precipitous withdrawals from Syria and Afghanistan by tweet before consulting with our partners or Congress, much less his own advisers? What will happen the next time we ask countries to help share the burden of fighting terrorism in a country far from home?

Part of our credibility gap is the result of our own domestic problems. How can our diplomats credibly encourage other governments to respect their own people’s basic rights when our president lauds authoritarian leaders, calls the press the enemy of the people, and undermines the legitimacy of his own judicial system? How will we persuade countries to act on the warnings of our intelligence agencies when the president regularly seeks to undermine and discredit them?

In Munich and later in London, I met with presidents, ministers, and other top officials from around the world and made clear that there remains a strong bipartisan commitment in Congress to stand by our longtime allies and partners. I emphasized that I would do my part to try to convince the administration that it is better to work in partnership with — instead of in opposition to — our allies.

The congressional delegation that traveled to Munich this year was named in honor of my friend Sen. John McCain, who long championed the historic ties between the U.S. and Europe. I am confident he would agree that we can keep America at the forefront while recommitting to the longstanding alliances that have advanced global peace and prosperity for 70 years. Failing to do so would be to the detriment of our own security.