Rep. Joaquin Castro, D-Texas, second from right, chairman of the Congressional Hispanic Caucus, speaks during a news conference after touring the Homestead Temporary Shelter for Unaccompanied Children with Rep. Debbie Mucarsel-Powell, D-Fla., left, R
Rep. Joaquin Castro, D-Texas, second from right, chairman of the Congressional Hispanic Caucus, speaks during a news conference after touring the Homestead Temporary Shelter for Unaccompanied Children with Rep. Debbie Mucarsel-Powell, D-Fla., left, R

Democrats in the U.S. House of Representatives are preparing to introduce a resolution challenging President Donald Trump's declaration of a national emergency at the country's southern border.

The resolution sponsored by Rep. Joaquin Castro of Texas is set to be filed Friday, and could get a vote in the full House by mid-March.

House Speaker Nancy Pelosi issued a letter Wednesday encouraging both Democratic and Republican lawmakers to sign on as co-sponsors and said the measure would "move swiftly."

Trump declared an emergency at the U.S.-Mexico border last week after Congress passed a border security package totaling nearly $1.4 billion but without fulfilling his calls for $5.7 billion to construct a border wall.

Border Patrol agent Vincent Pirro looks on near a border wall that separates the cities of Tijuana, Mexico, and San Diego, Feb. 5, 2019, in San Diego.
US States Sue Trump Administration in Showdown Over Border Wall Funds
A coalition of 16 U.S. states led by California sued President Donald Trump's administration on Monday over his decision to declare a national emergency to obtain funds for building a wall along the U.S.-Mexico border.The lawsuit filed in U.S. District Court for the Northern District of California came just days after Trump invoked emergency powers on Friday after Congress declined to fulfill his request for $5.7 billion to help build the wall that was his signature 2016 campaign promise.

Trump says a wall is necessary to stop immigrants and drugs from illegally entering the country. Opponents say a wall is an expensive and ineffective measure, and that border security money would be better spent on more customs agents and boosting screening technology at points of entry.

Police gather on the street during a protest against U.S. President Donald Trump's declaration of a national emergency to build a border wall, outside Trump International Hotel & Tower in Manhattan, New York, U.S. Feb. 15, 2019.
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Latest numbers reflect a deep political divide, with 51 percent of Americans polled opposing the emergency declaration, and 39 percent in favor

The House resolution has a strong chance of passing the Democrat-led House. Republicans control the Senate, so a number of members of Trump's party would have to go against him in order for the measure to pass there. If it does clear both chambers of Congress, it would go to Trump's desk to meet a certain veto.

FILE - President Donald Trump declares a national emergency in order to build a wall along the southern border during an event in the Rose Garden at the White House in Washington, Feb. 15, 2019..
Trump: 'Absolute Right' to Build Border Wall
U.S. President Donald Trump asserted Tuesday he had an "absolute right" to declare a national emergency to build a wall along the U.S.-Mexico border without congressional approval of funding for it.Sixteen states sued Trump late Monday in federal court in California where judges have overturned other Trump initiatives during his 25-month presidency.But the U.S.

In addition to the legislative challenge to Trump's declaration, there are also a number of legal challenges that have been filed in recent days. Those include lawsuits from a collection of 16 states that say they are being harmed because Trump is diverting money from other programs to pay for wall construction, as well as landowners whose property is in the potential wall's path.