President-elect Donald Trump has tapped House Republican Conference chair and longtime ally Rep. Elise Stefanik, of New York, to serve as ambassador to the United Nations.

Stefanik is Trump's first Cabinet pick for his second term in the White House.

“I am honored to nominate Chairwoman Elise Stefanik to serve in my Cabinet as U.S. Ambassador to the United Nations. Elise is an incredibly strong, tough, and smart America First fighter,” Trump said in a statement Monday.

Stefanik said she was "truly honored" by the nomination.

"I stand ready to advance President Donald J. Trump’s restoration of America First peace through strength leadership on the world stage on Day One at the United Nations," she said in a statement.

Her appointment was first reported by CNN.

Stefanik, 40, has been a staunch defender of Israel in its response to Hamas' Oct. 7 attacks and has been outspoken over the last year about antisemitism on college campuses. A day before last week's election, Stefanik reiterated her call for the defunding of the United Nations Relief and Works Agency for Palestine Refugees in the Near East because she alleges it has been infiltrated by Hamas.

Israel has accused staff members of the organization of participating in the Oct. 7 terror attacks, prompting it to fire at least 10 people. Israel's parliament voted in late October to ban the organization's operations.

Stefanik has served as the chairwoman of the House Republican Conference since May 2021, after then-Rep. Liz Cheney, R-Wyo., was ousted over her vocal criticism of Trump. Stefanik has served in the House since 2015 and represents New York's 21st Congressional District, which covers upstate New York, bordering Vermont and Canada.

Any appointments by Trump that lead to vacancies in the House could prove problematic for House Republicans. While they could maintain control of the lower chamber, an election outcome that NBC News has not yet called, their margin will be slim, and they struggled throughout the last Congress to maintain effective control of the body with few votes to spare.