Some 22,000 minors illegally crossed the Southern U.S. border in December, a number that government officials say bolsters the argument for building the president's promised border wall.

Of those 22,000 minors, roughly 5,000 were unaccompanied by a parent or guardian.

'Vulnerable populations are embarking on the dangerous journey north in record numbers putting themselves and minors in harm's way,' said Katie Waldman, a spokeswoman for the Department of Homeland Security.

Central American migrants cross the US-Mexico border fence from Tijuana to San Diego County as seen from Tijuana on December 27, 2018

In addition, more than 15,000 unaccompanied minors crossed the border in the first three months of federal fiscal year 2019 – which began October 1, 2018.

U.S. officials are calling the situation a humanitarian crisis, noting that there has been significant demand for medical treatment by immigrants, often related to the long journey they made to reach the border.

Wendy Young, president of Kids in Need of Defense, which represents migrant children, said the problem was being exacerbated by U.S. immigration policies introduced under the Trump administration.

'This is a humanitarian crisis that largely involves people fleeing extreme violence in Central America which means this is a refugee movement,' Young told DailyMail.com 'And the government's approach to treat this as a law enforcement challenge instead of a humanitarian challenge is the wrong approach.'

Waldman disagreed, saying the numbers are further indication that a border wall is needed, and criticized current immigration laws and a federal court that has ruled against the administration on several key cases.

'The lack of a physical barrier coupled with major loopholes from badly written laws and a terrible ruling from the Ninth Circuit act (as) a magnet for family units and unaccompanied alien children,' Waldman said.

The Ninth Circuit Court has been a thorn in Trump's side on immigration issues, striking down his original travel ban for Muslim countries, and more recently issuing a temporary restraining order against the administration's plan to refuse the right to apply for asylum to immigrants who cross the border illegally.

Trump has also sought to end the Ninth Circuit's Flores Settlement Agreement – a decades-long legal deal that provides minimum standards for caring for immigrant children in U.S. custody.

A migrant child sleeps while he is carried by family alongside fellow migrants who traveled from Central America with the intention of crossing into the U.S. from Tijuana, Mexico on December 14, 2018

In the last week of December alone, Customs and Border Protection referred 451 migrant for medical treatment, including 129 children under the age of five; 88 who were aged 6-14; and 42 between ages 15-17, officials said.

'Congress must act to fund the border wall, amend the 2008 Trafficking Victims Protections Reauthorization Act, and terminate the Ninth Circuit's Flores Settlement Agreement to stop the cycle of illegal immigration,' Waldman said.

Several migrant children have died while in U.S. custody – incidences that government officials have blamed on the condition the children were in when they arrived in this country.

'The tragic results of children losing their lives is also a reflection of the fact that this crisis is self-created,' Young said. ' The administration has adopted a policy of pushing people back into Mexico, living in substandard conditions and requiring them to wait several weeks or months ... Sadly we shouldn't be surprised that children are dying as a result.'