(CNN) Speaker of the House Nancy Pelosi urged members of Congress on Wednesday to back a resolution halting the national emergency declared by President Donald Trump to fund a border wall.

Pelosi's call to action comes as the White House plows ahead on transferring federal funds not contingent on Trump's declaration toward building a wall along the southern border, despite already facing several lawsuits

"I write to invite all Members of Congress to cosponsor Congressman Joaquin Castro's privileged resolution ... to terminate this emergency declaration using the termination mechanism within the National Emergencies Act," the California Democrat wrote in a letter to her colleagues.

"All Members take an oath of office to support and defend the Constitution," Pelosi added. "The President's decision to go outside the bounds of the law to try to get what he failed to achieve in the constitutional legislative process violates the Constitution and must be terminated. We have a solemn responsibility to uphold the Constitution, and defend our system of checks and balances against the President's assault."

Representatives have until 3 p.m. Thursday to sign the resolution, which will be introduced Friday, Pelosi wrote. The House will "move swiftly" under the National Emergencies Act to pass it before sending it to the Senate, she added.

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