WASHINGTON — Saying he could no longer be “complicit” in the Trump administration, Chuck Park, an eight-year State Department veteran most recently posted to a U.S. consulate in Mexico, last week became the latest American diplomat to publicly and pointedly call it quits.

“Over three tours abroad, I worked to spread what I believed were American values: freedom, fairness and tolerance,” Park wrote in an essay. “But more and more I found myself in a defensive stance, struggling to explain to foreign peoples the blatant contradictions at home.”

The ranks of the United States’ foreign policy establishment are being roiled once again by resignations, reports of partisan intimidation and looming massive cuts in foreign aid that critics in Congress and elsewhere contend weaken American diplomacy worldwide.

When Secretary of State Michael R. Pompeo took over the State Department 16 months ago, there was a surge in optimism that a dispirited corps would be reinvigorated after a tumultuous year of budget cuts and bungled management under former ExxonMobil CEO Rex Tillerson.

But morale is sinking amid signs that American foreign policy is now being dictated unchecked by a shoot-from-the-hip president and executed by a secretary of State with the political savvy to actually implement those controversial policies.

That includes efforts to essentially revamp the United States’ asylum programs, proceed with arms sales to Saudi Arabia despite bipartisan congressional opposition following the gruesome murder of a U.S.-based journalist in a Saudi consulate, and overturning decades of U.S. policy in the Middle East by moving the U.S. Embassy in Israel to the disputed city of Jerusalem.

In parts of the world and international venues where American influence was once king, the U.S. has lost influence or is not present, critics say. Pompeo has declined to get involved in a delicate dispute between Japan and South Korea, two key Asian allies whose cooperation is central to regional stability, and negotiations with nuclear-armed North Korea.

Pompeo will not attend this week’s Group of 7 meeting of the world’s top advanced democracies, leaving it to Trump — who last year stormed away from the summit and refused to sign a final document, the first time that has happened.

A communique this week from Western democracies offering support to the Hong Kong protesters facing off with China was signed by major world powers, but not the United States.

And in the coming days, the White House is expected to maneuver around legal hurdles to attempt to slash as much as $4 billion in U.S. foreign aid that supports crucial programs around the world, including peacekeeping missions and development, educational and human rights projects.

“We are not in a good place for dealing with the next super-crisis overseas, nor ongoing great power competition,” Barbara Leaf, a retired 34-year veteran of the foreign service whose last post was as ambassador to the United Arab Emirates, said on Twitter.

In an interview, she added, “We have lost decades of expertise vital to our national interests ... and we are stepping back a degree from the international engagement of the last 75 years that shaped” the world order.

For many diplomats like Park, the unconventional Trump approach has triggered an intense debate about whether to stay and promote good diplomacy, or leave an administration that violates their values. In social chat rooms and private conversations, they discuss what one diplomat called the “morality” of their work.

One of State’s most senior officials, the assistant secretary in charge of the Western Hemisphere, Kimberly Breier, abruptly resigned this month after reportedly clashing with White House advisor Stephen Miller over his aggressive immigration policies.

Several people said they expected additional departures in the coming weeks.

Another diplomat told The Times this week he was quitting in part because Pompeo’s State Department seemed to have little use for input from its experienced foreign service officers.

“We are serving a secretary of State who largely agrees with the president” instead of offering alternative viewpoints, said the diplomat, who is based in Latin America and requested anonymity because his resignation is pending. State’s “is a largely empowering voice,” he added.

Trump and Pompeo defend their policies, arguing the United States can no longer be the world’s police force or its benefactor. They say they are promoting a doctrine of “America first” that puts top priority on the prosperity and security of U.S. citizens.

But critics warn that could lead to U.S. isolation. “What we’re seeing, I think, is the institutionalization of America alone,” said Heather Conley, who heads the Europe program at the nonpartisan Center for Strategic and International Studies. “Other countries are trying to figure out who takes up the new mantle and [whether] can they hold on … until the U.S. returns to that leadership role, if it will.”

Speaking this week to the U.N. Security Council, Pompeo defended the administration’s conduct offoreign policy, saying it was “reviving” America’s leadership role by joining multilateral efforts that are “meaningful,” “effective” and “reflect the values of freedom-loving societies,” such as the battle against Islamic State.

But in State Department ranks, there are frustrations on other fronts as well. A new report by the inspector general’s office documents cases of Trump loyalists appointed to senior positions inside the department who went on to demand fealty to the administration and often berated and abused those they believed fell short.

The report recounted cases of “harassment” of career employees “premised on claims that they were ‘disloyal’ based on their perceived political views.”

Focusing on the State Department’s internal divisions over the United Nations and other multilateral organizations, investigators described a “negative and vindictive” environment in which one political appointee, senior advisor Mari Stull, punished and dressed down those she believed undermined Trump. She removed one senior official from the office and drove away dozens more, according to the report.

Stull, who left the administration this year, was formerly a food-industry lobbyist who came to the State Department from a wine blog she produced under the name Vino Vixen. She told those who complained that their objections were “pointless,” the report said, because “the Trump administration ‘has my back.’”

In cutting foreign aid, it remains unclear which programs will be targeted and how much will be lost. To slash the money, the White House is submitting the proposed cuts late in the fiscal year so that Congress will not have time to act. The “rescission” package, as it is known, freezes foreign aid money that Congress already approved for a 45-day review period. The fiscal year ends Sept. 30, meaning the money will almost certainly go unspent.

Times staff writer Jennifer Haberkorn in Washington contributed to this report.