The number of Venezuelans fleeing their country's economic and humanitarian crisis is expected to reach 5.3 million by the end of 2019 in what has become the largest exodus in modern Latin American history, the United Nations said Friday.

The U.N. High Commissioner for Refugees said that humanitarian organizations will need $738 million to provide migrants with critical services like food and emergency shelter as added stress is put on receiving nations.

"It is now vital that we stabilize the dire humanitarian situation affecting the millions of Venezuelans seeking protection and shelter across the continent," said the commissioner, Filippo Grandi.

In concordance with current migrant patterns, Colombia is expected to continue receiving the largest number of migrants, with over 2.2 million expected to have settled in the neighboring Andean nation by December 2019. Peru is likely to see the second largest influx, with nearly 1.4 million having arrived by the end of next year.

Ecuador and Brazil, in addition to other nations in the Southern Cone, Central America and the Caribbean, are also projected to see an increase in the numbers of Venezuelan migrants, though to a lesser extent. Estimates are based on government figures calculated for planning purposes as regional officials and aid groups determine their response.

"Beyond the most immediate humanitarian impacts of the largest displacement of people in the history of Latin America, there are other quite complex implications for which we were not prepared as a region," Eduardo Stein, the U.N.'s Joint Special Representative for Venezuelan refugees and migrants, wrote in the response plan's report.

Over three million Venezuelans have fled their country's soaring hyperinflation, food and medical shortages, and instability up until now, according to United Nations estimates. Those numbers are almost certainly an undercount, as government estimates often don't take into account migrants with no legal status.

Many of those fleeing Venezuela today represent the most vulnerable segments of the population and are undertaking perilous treks, including by foot, in order to reach their destination.

Once they arrive, many find themselves living sleeping on the floor in rooms cramped with other migrants and often still struggle to meet basic needs like food, education for children and health care.

A joint plan coordinated by the U.N. refugee agency and the International Organization for Migration includes 95 organizations in 16 countries and focuses on four priority areas including direct emergency assistance, protection, socio-economic and cultural integration and strengthening capacities of receiving nations.

The plan calls on donors, including international financial institutions, to play an important role in raising the $738 million and in supporting refugees, migrants and the nations receiving them.

The aid is aimed at helping 2.7 million people, most of whom are Venezuelan.

Countries around the region pledged at a recent meeting in Ecuador to formulate a response to the migration crisis including making a streamlined process for migrants so they can regularize their legal status.