Texas Gov. Greg Abbott sent a letter to President Biden Thursday formally requesting an appeal of the Federal Emergency Management Agency's (FEMA) denial of an emergency disaster declaration due to the massive influx of migrants at Texas' border with Mexico.

Abbott wrote to Biden on Sept. 20, asking the president to issue an emergency declaration for his state due to the increasingly difficult border crisis. However, days later on Sept. 29, FEMA denied the governor's request. 

"Texas will stand with the federal government in responding to this border crisis, but should not have to stand alone or withstand the financial burden without federal assistance," Abbott says in the formal appeal of FEMA's decision.

TEXAS GOV. ABBOTT ASKS BIDEN FOR FEDERAL EMERGENCY DECLARATION AMID BORDER CRISIS

"This crisis has taken a serious toll on the Texas border communities, first responders, and the local non-profit sector. Local officials and Texas citizens are fatigued and running out of resources to respond to the ongoing border crisis. The citizens of Texas are resilient and will continue to respond, recover, and mitigate against this crisis, but in order to expedite this process, federal assistance is needed for these vulnerable populations."

In his initial request, Abbott said the city of Del Rio is overwhelmed by over 16,000 Haitian migrants encamped under the International Bridge.

"Families, including infants and children, need food, water and medical supplies that the local government cannot supply," Abbott wrote. "Thousands of families are immobilized in 100-degree heat as their numbers continue to swell as they wait to be processed by the approximately 64 federal agents in the area. Individuals are camping in squalid conditions and bathing in muddy river water, causing great health concerns."

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Abbott noted that Del Rio's population is only 35,000 people, and that the city is not equipped to handle that many migrants.

Secretary of State Antony Blinken, Homeland Security Secretary Alejandro Mayorkas and Attorney General Merrick Garland will be in Mexico City Friday to discuss "security issues" with the Mexican government.

Fox News' Ronn Blitzer contributed to this report.