WASHINGTON — The Trump administration's top diplomat for Latin America has resigned amid internal disputes over immigration policy for the region, U.S. officials said Wednesday.

Two officials and a congressional aide said Assistant Secretary of State for Western Hemisphere Affairs Kimberly Breier stepped down earlier this week, although they offered differing reasons for her departure. They say Breier cited personal reasons for her decision, but the two officials suggested it was prompted by differences over a recent migration accord with Guatemala. The congressional aide said Breier's departure was mainly driven by family responsibilities.

Breier tweeted Thursday morning that it had been "an honor and a privilege" to serve in her role and gave her "profound thanks" to President Donald Trump and Secretary of State Mike Pompeo for the opportunity. She also thanked senior White House aides Ivanka Trump and husband Jared Kushner for their friendship.

It has been an honor and a privilege to serve as the Assistant Secretary of Western Hemisphere Affairs. I offer my profound thanks to @POTUS, @SecPompeo, and the administration for the opportunity to serve, and to @IvankaTrump and Jared Kushner for their friendship and support. https://t.co/aO6ZGFS0lY — Kimberly Breier (@WHAAsstSecty) August 8, 2019

The Washington Post, which first reported Breier's resignation, said she had clashed with the White House over the Guatemala accord that many human rights advocates oppose.

Pompeo said on Twitter later Thursday morning that Breier was stepping down to spend more time with her family and wished them well.

After 2+ years of late nights & constant travel, A/S Kim Breier will be stepping down to spend more time with her family. Kim's expertise, counsel & passion ensured our nation seized opportunities & got results. I’m grateful for her service & wish Kim, Peter, & Emma all the best. — Secretary Pompeo (@SecPompeo) August 8, 2019

In a tweet, Trump's daughter Ivanka thanked Breier for her "friendship and great service" and said she would miss working with her. The Mexican ambassador to the U.S., Martha Bárcena also tweeted thanks to Breier, praising their "constructive approach" in working together and acknowledging "your deep understanding of our country."

Dear Kim @WHAAsstSecty

we will miss you! The Embassy and I always worked with you and your team with a constructive approach and we acknowledge your deep understanding of our country. Thank you! @StateDept

@SecPompeo

@IvankaTrump

@washingtonpost — Martha Bárcena. (@Martha_Barcena) August 8, 2019

Breier is the second senior State Department official to leave the administration this month. Last week, Kiron Skinner, the department's director of policy planning, was removed from her post following complaints about her management style, officials said.

The Trump administration has struggled to fill numerous senior diplomatic positions and only recently were top diplomats for East Asia and the Pacific and the Middle East confirmed by the Senate. The posts of assistant secretary of state for South and Central Asia and for Europe are occupied by officials on an acting basis.

Breier, who specialized in Mexico, joined the Trump administration in October 2018, after a career in government and the private sector focused on Latin America. She had been praised for her insights and analysis of the region while serving on the National Security Council during the George W. Bush administration.

However, her refusal to testify before Congress even once during her 10-month tenure had irritated several lawmakers.

At a closed-door business meeting of the Senate Foreign Relations Committee just two weeks ago, Florida Republican Marco Rubio and Indiana Republican Todd Young expressed frustration that neither she nor anyone from her bureau would agree to testify at two planned hearings on Central America and Colombia, according to two Senate staffers. The staffers spoke on condition of anonymity because they weren't authorized to discuss the matter publicly.

Breier was known to have an ongoing feud with Mauricio Claver-Carone, her Western Hemisphere counterpart at the National Security Council, the two staffers said. They said she also was marginalized from playing a role in policy toward Venezuela — with immigration and trade, the most-pressing foreign policy challenge in the region — after Trump named Elliott Abrams as special envoy to the crisis-wracked country.