WASHINGTON, United States (AFP) — President Donald Trump has removed Admiral Linda Fagan — the first woman to lead one of the six US military services — as the head of the Coast Guard, with an official citing alleged "leadership deficiencies."

"She served a long and illustrious career, and I thank her for her service," acting Department of Homeland Security (DHS) secretary Benjamine Huffman said in a message Tuesday to the Coast Guard.

But a senior official from the DHS — which oversees the service — was far more critical, saying Fagan was dismissed "because of her leadership deficiencies, operational failures, and inability to advance the strategic objectives of the US Coast Guard."

The admiral failed to address border security threats, mismanaged acquisitions, including helicopters, and put "excessive focus" on diversity, equity and inclusion programs, the official said on condition of anonymity.

There was also an "erosion of trust" in the Coast Guard due to its handling of an investigation into sexual assault allegations.

"The failure to adequately address the systemic issues exposed by this investigation has underscored a leadership culture unwilling to ensure accountability and transparency," the official added.

Review of senior officers

Trump and other Republicans have long railed against government programs aimed at fostering diversity, and border security is a key priority for the president, who declared a national emergency at the US frontier with Mexico on Monday, the first day of his new term.

Trump has had a contradictory relationship with America's armed forces, at times lauding their power but also claiming they were depleted and in need of rebuilding.

He has clashed with former top US military officer Mark Milley, with the retired general's portrait at the Pentagon removed on the same day that Trump was sworn in for his second term.