In a sudden move, Indian-American US Ambassador to the United Nations Nikki Haley resigned on Tuesday, becoming the latest casualty in the fragile Trump administration just weeks ahead of the crucial mid-term elections.

President Donald Trump has accepted her resignation, US media reported.

Trump has tweeted that he has a "big announcement" with Haley in the Oval Office at 10:30 a.m.

The reason behind her resignation was not immediately clear.

Haley, 46, was the senior most Indian-American official in the Trump administration.

She was confirmed as UN Ambassador four days after Trump was inaugurated in January 2017. She had scripted history by becoming the first-ever Indian-American to be appointed to a cabinet-level post in any US administration.

The daughter of Indian immigrants from Punjab, Haley was the first woman tapped by Trump for a top-level administration post during his transition to the White House.

Haley's nomination was a turning point for the Indian-American community which is increasingly playing a greater role in American politics.

She was critical of Trump during the primary campaign and had backed Senator Marco Rubio in the Republican primary. However, before the general elections, she switched her position, saying she would vote for Trump.

Born Nimrata "Nikki" Randhawa, Haley is the first minority and female governor of South Carolina, a deeply conservative state with a long history of racial strife.

She is the first Indian-American woman Governor and the second Indian-American governor of any State. Prior to becoming governor, she represented Lexington County in the South Carolina House of Representatives from 2005 to 2011.

Prior to dedicating her life to public service, Haley worked at her family business.

Haley and her husband, Michael, a Captain in the Army National Guard and combat veteran who was deployed to Afghanistan’s Helmand Province, have two children, Rena and Nalin.