Get breaking news alerts and special reports. The news and stories that matter, delivered weekday mornings.

With the partial government shutdown stretching into a third week, President Donald Trump is slated to deliver a prime-time Oval Office address to the nation on Tuesday "on the humanitarian and national security crisis on our southern border."

Over his past two years in office, Trump has made a number of claims around the issue of immigration, many of them false and misleading, according to NBC News reporting. Here are some of his most significant assertions, and the facts.

Claim: Building a wall will prevent drugs from flowing into the country.

The facts: It's unlikely that a wall would stop illegal drugs from coming into the U.S., since the bulk of drugs coming across the southwest border do so through legal ports of entry, hidden in cars or tractor-trailers, according to a 2015 report by the Drug Enforcement Administration.

The Trump administration knows this. Then-Department of Homeland Security Secretary John Kelly — who went on to become White House chief of staff — said in April 2017 that illegal drug traffic “mostly comes through the ports of entry.”

A wall would have no effect on those legal entryways.

Claim: Federal workers want the wall.

The facts: Not according to available public surveys.

A poll by GovExec, a publication aimed at employees of government departments and agencies, conducted Dec. 27-28, 2018, found that only about 30 percent of federal workers support a wall. About 71 percent of them oppose the shutdown.

Claim: Much of the wall has already been built.

The facts: This is false.

The White House has not yet built any new section of border fencing or wall. Trump's administration has repaired and replaced old sections of border barrier with the same kind of fencing the president derided as a candidate as insufficient.

Claim: Former presidents told Trump they should have built a wall.

The facts: Spokespeople for the four living ex-presidents have denied this claim to NBC News.

Claim: Nearly 4,000 suspected terrorists have been apprehended at the southern border.

The facts: This claim, made by the White House in recent days, is contradictory to government data obtained by NBC News.

U.S. Customs and Border Protection encountered only six immigrants at ports of entry on the U.S-Mexico border in the first half of fiscal year 2018 whose names were on a federal government list of known or suspected terrorists, according to Customs and Border Protection data provided to Congress in May 2018 and obtained by NBC News. Nearly seven times as many immigrants who were on terror watch lists were stopped on the nation's northern border with Canada.

On Tuesday, Vice President Mike Pence said that "3,000 special interest aliens were apprehended trying to come into our country" in 2018 and that "we apprehended 17,000 people with criminal records attempting to come over the southern border last year alone."

But "special interest aliens" means something different than "known or suspected terrorists." It only means that a person has travel patterns that raised a red flag based on where they came from, and there was something that made CBP take a second look at them. According to former high level DHS officials, the working definition is someone who exhibits strange travel patterns and originates from a country outside of the Western Hemisphere. They often are not included on terrorist databases.

Let our news meet your inbox. The news and stories that matters, delivered weekday mornings. This site is protected by recaptcha

Additionally, Pence's 17,000 number needs more context. CBP encountered 16,831 foreigners with criminal convictions in an 11-month period during fiscal year 2018, and 63 percent of them were encountered at legal ports of entry and barred entry. The other 37 percent, 6,259 people, were arrested by border patrol agents.

Notably, the crimes are a mix of violent and nonviolent crimes. Approximately half of those arrested by border patrol agents were convicted of illegal entry or re-entry; 98 were convicted of illegal weapons possession, transport, or trafficking, while 1,062 were convicted of driving under the influence.

Claim: Mexico is paying for the wall with the new trade deal.

The facts: Trade experts have told fact checkers that this is false, too.

There's nothing in the new trade deal that earmarks funds for the border wall; revenue raised by tariffs are federal dollars that must be appropriated by Congress.

What’s more, the trade deal must still be ratified by legislators in the three countries and would not take effect until 2020 at the earliest.

Claim: The wall is needed to stop violence at the border.

The facts: Trump's own administration determined that spillover violence "does not represent a significant trend of concern" in a 2017 report. Asked about the data, Homeland Security Secretary Kirstjen Nielsen told NBC News she hadn't seen it.

Claim: Previous administrations separated families at the border, too.

The facts: This claim is misleading.

Trump and other administration officials have suggested that his policy of separating families at the border — which sparked widespread public outrage in spring 2018 — was simply a continuation of what previous administrations, including President Barack Obama's, have done. Immigration experts, advocates, and former Obama administration officials said that's wrong. There was no widespread Obama-era policy of separating parents and children

There were some cases in previous administrations where families were separated, experts told NBC News, but it was the exception, not the rule.

Claim: Trump can declare a national emergency to get wall money.

The facts: It's true that the president has the authority to declare that the country is in a state of national emergency, generally.

But when it comes to where the money for the wall comes from, it’s more complicated, and any move is likely to be met by a court challenge.

Legal experts told NBC News that Trump may have a legitimate case, but it depends on the legal arguments that his administration makes and where he tries to draw those funds from.

Claim: Illegal immigration costs America more than $200 billion.

The facts: Immigration policy experts across the political spectrum told NBC News that while undocumented immigrants do incur costs at the federal and state level, they also pay taxes. Those experts said the true cost, while difficult to ascertain, would be nowhere near the billions Trump has claimed.

Claim: Existing border wall sections caused "illegal traffic" to decline.

The facts: This claim needs more context, and no new sections of "wall" have been built.

Trump has pointed to accurate data — such as the fact that illegal traffic dropped 92 percent after border fencing was constructed in San Diego in 1992 — to back up his calls for a border wall. The numbers appear to be correct, albeit cherry-picked. They also require context: Traffic dropped 92 percent there over 23 years amid a border-wide trend of fewer border crossings. What's more, he’s celebrating the wins of past administrations and the kind of border fencing he's long said was not enough.

Claim: Migrants are bringing disease into the U.S.

The facts: There's no evidence of this, according to a report released last month.

A group of 24 medical experts spent two years analyzing whether migration spreads disease, as well as looking into the effects that migrants have on health in their new homelands. Their conclusion: Immigrants make up a significant portion of the health care workforce, and migration boosts economies overall.

Claim: ICE is hunting down dangerous people and MS-13 gang members.

The facts: This is partly true.

Immigration and Customs Enforcement does target undocumented immigrants deemed dangerous by law enforcement, arrest and deport them, but it's a small portion of their overall work. In fiscal year 2017, there were more than 181,000 arrests. Seventeen percent of those arrests were arrests targeting criminals, and 2.6 percent of the total were gang-related arrests. The rest were administrative arrests.

As for MS-13, there were 796 arrests related to MS-13 in fiscal year 2017.

Claim: Fake news ignores crimes committed by immigrants.

The facts: Trump has previously distorted facts to substantiate this claim, but there is no evidence that foreign nationals or immigrants commit more crimes than native-born Americans.

Claim: "Catch and release" lets immigrants stay in the U.S. indefinitely.

The facts: This is misleading, since there is no law or hard and fast policy called "catch and release" that gives undocumented immigrants carte blanche to remain in the U.S. As NBC News has reported, the term originally became popular during the Bush administration to describe the practice of releasing immigrants from detention while they await immigration court proceedings, in part because there were not enough detention facilities to hold immigrants pending immigration court proceedings.

Immigration experts say the practice is no longer common. The White House has used the term to blast the protections afforded to children and families seeking asylum in the U.S., complaining that the government can't detain asylum seekers indefinitely.