
Mexico has dispatched two Boeing 727s full of federal police officers to its southern border, as the country prepares for the arrival of a migrant caravan of thousands from Central America.

Five hundred federal police officers in riot gear arrived on Wednesday in Tapachula, Chiapas on the border with Guatemala, where some 4,000 migrants are now marching northward.

The presence of federal forces on the southern border of the country is not to stop migrants from crossing the border, but to help immigration officials maintain order, Mexican Federal Police Commissioner Manelich Castilla Craviotto told Noticeros Televisia.

'The INM reiterates its unrestricted commitment to respect the human rights of migrants,' said Mexico's National Institute of Migration, a government agency that controls and supervises immigration.

U.S. President Donald Trump warned Thursday that he will use military force to seal the U.S-Mexico border unless Mexico intervenes.

'I must, in the strongest of terms, ask Mexico to stop this onslaught – and if unable to do so I will call up the U.S. Military and CLOSE OUR SOUTHERN BORDER!' Trump wrote on Twitter.

The Mexican government dispatched two Boeing 727s filled with police to the country's southern border on Wednesday

The federal police will attempt to keep order at Mexico's border with Guatemala as a caravan of immigrants marches north

Migrants with the Honduran flag take part in a caravan towards the United States in Chiquimula, Guatemala on Wednesday

Honduran migrants continue their travel from Chiquimula towards the department of Zacapa, Guatemala on Wednesday

Meanwhile, the massive caravan continued its trek north in a bold attempt to reach the United States, defying threats from President Donald Trump to stop aid to countries that let them pass.

The group reached Guatamala City on Wednesday, about 180 miles from the Mexican border, where Mexican officials greeted leaders of the march.

Mexico's Foreign Ministry said that at the meeting, 'reliable and updated information was provided on the procedures required by the Government of Mexico to allow regular entry of migrants to Mexico and the process to be followed for those who wish to request recognition of refugee status.'

The officials also advised the migrants that there was no transit visa that would allow them to cross to the northern border with the US, according to the Foreign Ministry.

President Donald Trump threatened on Thursday to use the U.S. military to close the southern border unless Mexico helps stop flow of Central American immigrants traveling from the south

The president renewed his complaint that the Guatemalan, Honduran and Salvadoran governments are doing nothing to stop a massive flow of people northward, 'INCLUDING MANY CRIMINALS'

Honduran migrants take part in a caravan towards the United States in Chiquimula, Guatemala on Wednesday

Honduran migrants, part of a caravan trying to reach the U.S., are pictured during a new leg of their travel on Wednesday

Honduran migrants continue their travel from Chiquimula towards the department of Zacapa, Guatemala on Wednesday

Honduran migrants who are traveling to the U.S. as a group get a free ride in the back of a driver's truck through Guatemala

Honduran migrants bound to the U.S border climb into the bed of a truck in Zacapa, Guatemala on Wednesday

Honduran migrants get a free ride in the back of a trailer truck flatbed, as they make their way through Teculutan, Guatemala

Honduran migrants, part of a caravan trying to reach the U.S., are pictured on a truck in Zacapa, Guatemala on Wednesday

Trump - who took aim at Honduras, Guatemala and El Salvador on Tuesday - kept up his attacks on the march the following day, saying it should be an important issue for Republican candidates in the upcoming midterm elections.

'Hard to believe that with thousands of people from South of the Border walking unimpeded towards our country in the form of large caravans, that the Democrats won't allow legislation that will allow laws for the protection of our country.'

'Republicans must make the horrendous, weak and outdated immigration laws, and the border, a part of the midterms,' the President said on Twitter.

In a church-sponsored shelter in the center of the Guatemalan capital on Wednesday, a vanguard group of around a thousand Hondurans took refuge, exhausted by tramping for hours in the sun and rain.

Immigrants, part of a migrant caravan, carry a Honduran flag on their journey on Wednesday in Guastatoya, Guatemala

The caravan of Central Americans continues their journey through Guatemala, planning to enter Mexico in route to the U.S.

Trump has threatened to withhold aid to Central American countries that don't stop the migrants in their journey north

'This is the beginning of an avalanche that is coming, because we can no longer endure so much violence,' said Denis Contreras, who fled Honduras with his sister and two nieces.

Contreras, wearing the red shirt of the Honduran national soccer team, said there's no going back to his Central American country he says is strangled by poverty and violence. Leaving the country 'is already frowned upon' by Honduras' gangs and returning would be a death sentence, he said.

Their objective now is to regain strength and press on towards the border with Mexico.

A second group moved across the border into Guatemala on Monday afternoon and have reached the city of Esquipulas.

A third of more than 400 Hondurans crossed El Salvador to join up as well, according to Salvadoran migration officials.

The original throng of more than 4,000 migrants left last Saturday from the northern Honduran city of San Pedro Sula after organizing themselves on social media.

Honduran migrants aboard a truck arrive in in Guatemala City, while taking part in a caravan towards the United States

Honduran migrants aboard a truck, take part in a caravan towards the United States in Zacapa, 145 km east of Guatemala City

Honduran migrants, part of a caravan trying to reach the U.S., cling to a truck during a new leg of travel in Zacapa, Guatemala

On Monday, a large contingent of police on the Guatemalan border tried to turn them back, but after an hours-long standoff, the marchers prevailed and managed to reach Esquipulas. They moved on in smaller groups to Guatemala City.

Maria Ramos said she decided to join the march north after seeing the huge group pass by her village of Ocotepeque on the Guatemalan border.

'When we saw them go by, we decided to leave as well,' said the Honduran woman. Her family was barely surviving on maize and beans in the arid border region, she said.

Meanwhile, the Honduran Observatory of Human Rights expressed 'serious concern' over the detention of journalist and migrants' rights defender Bartolo Fuentes on the Guatemalan border as he accompanied the caravan.

Guatemalan President Jimmy Morales told reporters his country was working with humanitarian organizations to provide food and shelter for the migrants.

Migrants from the caravan queue to receive food and shelter at the 'Casa del Migrante' (Migrant's House) in Guatemala City

Migrants queue to receive food and shelter at the 'Casa del Migrante' (Migrant's House) in Guatemala City on Wednesday

Honduran migrants, part of a caravan trying to reach the U.S., rest at a school being used a shelter in Guatemala City

But he said the 'unregistered massive influx' was putting 'people and countries at risk.'

'We cannot ensure that everyone has Honduran nationality or origin, nor that they have the destination they claim to have.' Many are at risk from human traffickers, he warned.

Morales said he discussed the crisis with Honduran counterpart Juan Orlando Hernandez and US Vice President Mike Pence.

In a makeshift dormitory at the shelter's gymnasium, Maria Ramos, 43, ate breakfast cereal with her 15-year-old daughter before leaving for a bus terminal to travel to the border with Mexico.

A Honduran migrant looks on as she rests along other fellow nationals at a school being used a shelter in Guatemala City

Honduran migrants, part of a caravan trying to reach the U.S., rest at a school being used a shelter in Guatemala City

Migrants rest at a school being used a shelter in Guatemala City on Wednesday as they approach the Mexican border

They plan to reach Mexico's southernmost state of Chiapas, whose governor Manuel Velasco said he would welcome migrants despite a federal government warning that undocumented migrants would be stopped at the border.

The migrants' dream is to get asylum in the United States, work and help their relatives who stayed behind, said Sairi Bueso, 24, pushing her two-year old daughter in a pram.

With a homicide rate of 43 per 100,000 inhabitants, Honduras is considered one of the world's most violent countries, mainly due to gangs and drug trafficking, a situation largely mirrored in neighboring Guatemala and El Salvador.

In addition, 68 percent of Honduras' nine million population live in poverty, according to UN data.