Image copyright EPA Image caption Mr Trump wants to temporarily ban visas from countries with poor vetting

Republican presidential nominee Donald Trump has unveiled his latest plans for immigration screenings. How will it work?

The proposal, outlined in a speech in Ohio, includes temporarily suspending visas from countries with terrorist ties as well as introducing an ideological test for those entering the US.

Though Mr Trump has yet to outline which countries would be included on the list, he told supporters at the rally he would "ask the State Department and Department of Homeland security to identify regions where adequate screenings cannot take place".

The billionaire businessman said the aim of his latest plan is to destroy the so-called Islamic State (IS), adding that he would work with any countries that share that mission.

Mr Trump also proposed an ideological test for those entering the US, focusing on issues such as religious freedom, gender equality and gay rights.

The government, he said, would use those test responses as well as social media and interviews with friends and relatives to determine whether a candidate supports American values. It is unclear how the test responses would be assessed.

Is this a revision of his Muslim ban?

Mr Trump's immigration plan has taken shape throughout his campaign, beginning with his call for a blanket ban on all Muslims entering the country in December 2015.

The proposal drew condemnation from both Democrats and Republicans, including from his running mate Indiana Governor Mike Pence.

The New York developer changed his tune after a shooting at an Orlando nightclub in June, saying he would temporarily ban visas from countries with a history of terrorism against the US and other western nations.

Though the latest iteration would issue a ban on certain countries, some immigration experts say it still unfairly targets Muslims.

A Virginia immigration lawyer, Hassan Ahmad, points out that Mr Trump's policy seems to reinforce the rise of xenophobic sentiment, with Muslims bearing the brunt of proposals such as implementing ideological tests.

Kevin Johnson, dean of the UC Davis Law School, says the concept of ideological litmus tests recalls the Cold War era and the use of immigration laws to regulate the ideologies of people coming to the US.

Mr Trump did, in fact, invoke Cold War legislation in his speech, noting that the "time is overdue to develop a new screening test for the threats we face today".

"Using our immigration laws to screen out views we don't agree with seems arguably un-American in terms of our devotion to free speech rights," Mr Johnson said.

Media playback is unsupported on your device Media caption What is Trump's 'extreme vetting' plan?

What countries would be affected?

While it is unclear which countries would fall under Mr Trump's temporary ban, a Trump campaign official told the BBC to look at the current administration's lists of countries with terrorism ties.

According to the State Department's annual assessment on global terrorism, 12 countries provide "terrorist safe havens". These countries include: Somalia, Mali, Libya, Egypt, Iraq, Lebanon, the Philippines, Indonesia, Malaysia, Afghanistan, Pakistan and Yemen.

The State Department has also designated 14 countries where terror networks such as IS and al-Qaeda have established operations, including Turkey, Nigeria and Russia.

The US also lists Iran, Sudan and Syria as state sponsors of terrorism, bringing the total number of countries with terror links to 29 nations.

But if Mr Trump were to follow the State Department's list of other nations with smaller, established terrorist cells - which includes France, Belgium and the UK - that would bring the total to 40 nations which could fall under his ban.

However, a Trump campaign adviser told the BBC that Mr Trump would not mention specific countries until he receives full national security briefings and would instead focus on forming partnerships with governments and other agencies to strengthen the vetting process.

How is Mr Trump's plan different from the current system?

As experts point out, the US has rigorous vetting processes in place when it comes to immigration, and particularly, refugees - a group that Mr Trump has targeted in campaign speeches.

"There is a tremendous amount of vetting that takes place today," said Doris Meissner, a former commissioner of the Immigration and Naturalization Service, or the predecessor to the Department of Homeland Security's Immigration and Customs Enforcement (ICE).

Ms Meissner, a current senior fellow at the Migration Policy Institute, said the US has modernised screening databases to include criminal information, terrorist watch lists and other intelligence shared between the US and other countries.

The US has spent an enormous amount of time upgrading its systems, she said, and it continues to do so with a "renewed sense of cooperation" with other western countries in the wake of the attacks in Paris and Brussels.

Media playback is unsupported on your device Media caption Donald Trump: "I call it extreme, extreme vetting."

But while the US focuses on individually screening whether someone should be excluded based on terrorist activity, Mr Trump's plan appears to issue a blanket approach, Mr Johnson said.

"Usually, more focused individualised inquiries tend to bear more fruit when it comes to protecting people's security," he added.

Mr Trump's blanket approach echoes a programme implemented by US officials following the 11 September attacks, Mr Ahmad noted.

In 2002, the US created "Special Registration," a programme requiring Arab and Muslim men to register with authorities with the aim of uncovering terror links.

However, as Mr Ahmad notes, of the 25 countries listed in the programme, 24 were predominantly Muslim nations (except for North Korea).

The programme yielded little results, with only 11 of the more than 85,000 men registered in the first year found to have a link to terrorism, the New York Times reported.

But even so, the Bush administration's immigration policies did not issue temporary blanket bans as Mr Trump has suggested, Mr Johnson added.

"When you have blanket approaches, you generally get less effective security because you can't spend your time and effort on where the real problems are," Ms Meissner said.

Will Mr Trump's plan make the US safer?

Mr Trump vowed to "aggressively pursue joint and coalition military operations to crush and destroy ISIS" while also only allowing "those who share our values and respect our people" to enter the US.

But will his proposals strengthen US national security?

Experts seem to think his pledges are still too opaque to tell.

"It is not clear to me that there is any security benefits from either ideological exclusions or blanket exclusions from people from particular countries," Mr Johnson said.

Mr Ahmed describes his plan as "an act of security theatre".

"We already have a vetting system and it's focused on what people actually do rather than what their Facebook status says," he said.

Using social media and ideological tests also opens up the vetting process to misinterpretation, Ms Meissner added.

"Interviews with friends and family, vetting to under stand people's support for American values," she said, "Those are highly subjective factors."