Pompeo told reporters en route to Iraq that he planned to meet with Iraqi leaders in response to reports that Iran is "escalating their activity." He cited potential threats to U.S. troops in the country.
"This would be an effort to take American forces out that continue our campaign against ISIS, something that's incredibly important to the Iraqi government," Pompeo said, using an acronym to describe the Islamic State.
"It certainly is the case that if American interests in Iraq were threatened, it would impact Iraq as well."
Pompeo's trip to Iraq comes one day after the U.S. Department of Defense deployed the USS Abraham Lincoln Carrier Strike Group and a bomber task force to the Middle East in response to threats to U.S. troops by Iran or its allies.
Tensions with Iran have skyrocketed in the past week since the Trump administration ended waivers that allowed some countries to continue buying Iranian crude oil despite U.S. sanctions. That means China, India, Japan, South Korea and Turkey can no longer buy crude oil from Iran, putting increased pressure on Tehran.
The United States also officially designated Iran's Islamic Revolutionary Guard Corps as a terror group, which prompted Iran to name U.S. forces as terrorists as well.
The United States has forces in both Iraq and Afghanistan, which neighbor Iran to the west and east, respectively.
In April, Iranian President Hassan Rouhani called on Mideast nations, including Iraq, to collectively oppose the United States for supporting Israel. He said U.S. military involvement in Afghanistan, Iraq, Syria and Yemen has sowed "misery, agony and carnage."
Earlier in the day, State Department spokeswoman Morgan Ortagus offered no specific details about why the office canceled the Berlin meeting, which was expected to address Russia, China and Syria.
"Unfortunately, we must reschedule the Berlin meetings due to pressing issues," Ortagus said in a statement tweeted by the U.S. Embassy in Berlin. "We look forward to rescheduling this important set of meetings. The secretary looks forward to being in Berlin soon."
Merkel's office said the meeting would no longer happen "because of the visit's cancellation by the U.S. side."
Journalists traveling with the State Department said they were not told where they would go next as part of Pompeo's five-day trip, which includes London and Nuuk, Greenland, later in the week.
Nicholas Sakelaris contributed to this report.