The top US security official on Tuesday said Donald Trump’s proposal to ban Muslims from entering the United States was not only offensive but would undermine national security by thwarting efforts to connect with the Muslim American community.

‘It is irresponsible to do this and contrary to our national security efforts,’ US Homeland Security Secretary Jeh Johnson said in an interview on MSNBC in response to the Republican presidential candidate’s proposal to ban Muslims from coming into the country.

‘We are renouncing and rejecting his remarks,’ he told the television network, referring to Trump, who on Monday said if he wins his party’s nomination in the 2016 race for the White House and is elected president he would not allow Muslims to enter the county.

Separately, US Secretary of State John Kerry also said Trump’s comments were not constructive.

Johnson, who has previously declined to comment on the presidential race and earlier had declined to react to Trump’s plan, said he had reconsidered and that as head of US security efforts he was obligated to speak out now.

He said the Republican front-runner’s proposed ban was ‘irresponsible - probably illegal, unconstitutional and contrary to international law — un-American, and will actually hurt our efforts at homeland security.’

Trump has said such a ban is ‘common sense’ in the wake of last week’s shooting in San Bernardino, California, by a couple who authorities say were Muslims who had become more radical, as well as last month’s attacks in Paris that were claimed by Islamic State and left 130 dead.

On Tuesday, Trump defended his plan even as a growing chorus of critics, including other Republicans, rejected it.

Johnson said that while US President Barack Obama has acknowledged a new phase in the fight against militant groups like Islamic State, it was critical to build relationships with Muslims, not alienate them.

‘I want people in Muslim communities across this country to know that the president and I, members of this administration — and obviously a number of Republicans and Democrats - do not believe this, do not feel the way Mr. Trump feels,’ he told MSNBC.

Banning the world’s 1.6 billion Muslims from entering the United States was also unrealistic, Johnson said. Especially in the United States, Muslims represent a diverse community that includes African-Americas as well as those from many other countries such as Indonesia and Egypt, among others, he added.

‘We cannot vilify all Muslims,’ he said.