Attorney generals from 15 US states and the District of Columbia issued a strongly worded joint statement against Donald Trump's "unconstitutional, un-American and unlawful Executive Order" on Sunday (29 January).

The president's order signed on Friday (27 January) temporarily bans citizens from seven majority Muslim nations – Iran, Iraq, Libya, Somalia, Sudan, Syria and Yemen – from entering the US for 90 days.

It also suspends all refugee admissions for 120 days and bans Syrian refugees indefinitely, triggering widespread confusion, an intense backlash and international condemnation.

The chief legal officers criticised the action and vowed to "work together to ensure the federal government obeys the Constitution, respects our history as a nation of immigrants, and does not unlawfully target anyone because of their national origin or faith." Attorney generals from California, New York, Massachusetts, Washington, Iowa, Maine, Hawaii and other states signed the joint statement.

Trump defends travel ban

As criticism of the restrictive travel ban continued to mount from rights groups, celebrities, politicians and the general public, Trump stood by the controversial executive order. On Sunday, he tweeted: "Our country needs strong borders and extreme vetting, NOW. Look what is happening all over Europe and, indeed, the world – a horrible mess!"

He added: "Christians in the Middle-East [sic] have been executed in large numbers. We cannot allow this horror to continue!" According to a CNN report, a Syrian Christian family were forced to get back on a flight to Doha after arriving in Philadelphia on Saturday (28 January) despite having all the proper documentation.

Sarah Assali, who was waiting to welcome her relatives, said: "We're all feeling a lot of anger, a lot of disappointment in our government ... It's against our ethics as Americans."

A statement from Trump released by the White House said: "My policy is similar to what President Obama did in 2011 when he banned visas for refugees from Iraq for six months. The seven countries named in the Executive Order are the same countries previously identified by the Obama administration as sources of terror.

"To be clear, this is not a Muslim ban as the media are falsely reporting. This is not about religion – this is about terror and keeping our country safe," the statement continued.

Amid widespread confusion over the ban, senior Trump advisor Kellyanne Conway leapt to defend the measure, saying that chaos at airports is a "small price to pay" for extra security. "325,000 people from overseas came into this country just yesterday through our airports," she told Fox News Sunday.

"You're talking about 300-and-some who have been detained or are prevented from gaining access to an aircraft in their home countries and must stay for now. That's 1%, and I think in terms of the upside being greater protection of our borders of our people, it's a small price to pay," added Conway.

Comments from White House chief of staff Reince Priebus' heaped confusion on the status of green card holders after he appeared to row back on a key part of the immigration order. Priebus first told NBC's Chuck Todd that "as far as green card holders moving forward, it doesn't affect them".

But after further questioning on whether the order impacts green card holders, Priebus said: "Well, of course it does. If you're traveling back and forth, you're going to be subjected to further screening."

Priebus rejected claims that the process of implementing the order had been chaotic. In a joint press release, Republican senators John McCain and Lindsey Graham said: "It is clear from the confusion at our airports across the nation that President Trump's executive order was not properly vetted. We are particularly concerned by reports that this order went into effect with little to no consultation with the Departments of State, Defense, Justice, and Homeland Security.

"This executive order sends a signal, intended or not, that America does not want Muslims coming into our country. That is why we fear this executive order may do more to help terrorist recruitment than improve our security."

Trump's order also targets those who have nationality or dual nationality of Iran, Iraq, Libya, Somalia, Sudan, Syria and Yemen. While the status of those who shared dual nationality from allied countries such as the UK was initially unclear, the Foreign and Commonwealth Office (FCO) has now issued guidelines.

Department of Homeland Security (DHS) Secretary John Kelly later issued a statement approving the admission of green card holders. He said: "In applying the provisions of the president's executive order, I hereby deem the entry of lawful permanent residents to be in the national interest.

"Accordingly, absent the receipt of significant derogatory information indicating a serious threat to public safety and welfare, lawful permanent resident status will be a dispositive factor in our case-by-case determinations."

Read the FCO's statement in full below:

How are celebrities reacting?

Celebrities have joined a rising chorus of criticism against Trump's travel ban. Here's what they have to say: