"Looking forward to sharing with you how my family is more SAFE and more SECURE because of President Trump. See you all on Tuesday night," Pompeo, who has embarked on a four country trip, tweeted on Sunday.

Critics said that Pompeo's upcoming remarks break the tradition of keeping the chief US diplomat out of the party politics, reports Xinhua news agency.

"It is unprecedented in modern times for a Secretary of State to address a political convention," tweeted Nicolas Burns, a professor at Harvard Kennedy School who once served as undersecretary of state for political affairs under George W. Bush's administration.

"This is not wise at a time when our chief diplomat should be focused on restoring America's lost global credibility."

A State Department spokesperson defended Pompeo, saying her "would address the convention in his personal capacity. No State Department resources will be used".

US media reports said that Pompeo recorded his RNC address on Monday from the rooftop of King David Hotel in Jerusalem.

"At a time when peace and security in Middle East is so tough, Jerusalem should not be a prop for the RNC, and @SecPompeo should not be tarnishing the office of SecState. Unprecedented and wrong," tweeted Wendy Sherman, a senior State Department official under Bill Clinton and Barack Obama.

Pompeo's action might also violate a State Department policy he approved months ago.

Politico news on Monday obtained an email that Pompeo's deputy Stephen Biegun sent to State Department employees in February, an instruction in which he said: "Senate-confirmed Presidential appointees may not even attend a political party convention or convention-related event."

Pompeo choosing Jerusalem as the speech venue was widely seen as a calculation to woo evangelical Christian voters, as President Donald Trump said last week that he moved the capital of Israel to Jerusalem for evangelicals.

"Pompeo -- arguably worst Secretary of State in modern period is also most politicized/partisan," said Aaron David Miller, a senior fellow at the Carnegie Endowment for International Peace.

Besides Pompeo, First Lady Melania Trump will also address the RNC on Tuesday night from the recently renovated Rose Garden of the White House.