(Reuters) - The U.S. government on Monday urged a federal appeals court to issue an order blocking a lawsuit over climate change brought by a group of Oregon teenagers, warning that allowing it to go forward could lead to a constitutional crisis.

At a hearing before the U.S. Court of Appeals for the 9th Circuit in San Francisco, Eric Grant, a lawyer with the U.S. Department of Justice, said an extraordinary order would be justified to block the lawsuit, which names President Donald Trump and members of his cabinets as defendants.

“According to the plaintiffs’ complaint virtually every U.S. citizen has the right to sue virtually any government agency,” said Grant. Allowing the litigation would distract the executive branch from performing its duties, he added.

Filed in 2015 in federal court in Oregon, the lawsuit by 21 teenagers claims government officials and oil industry chief executives knew about the causes and effects of climate change but nevertheless carried on with policies that perpetuated it, violating the plaintiffs’ constitutional right to live in a habitable climate.

The lawsuit originally named President Barack Obama and members of his administration, but the defendants were substituted with Trump and his appointees in February 2017, including all cabinet secretaries and several agency heads.

A federal judge in Oregon ruled in 2016 that the case could move forward, setting a trial date for February 2018. The U.S. government requested and was granted a stay to allow it to ask the 9th Circuit for an extraordinary order, called a writ of mandamus, to block the trial from proceeding.

Grant called the claims “meritless” and said the case would cause a “constitutional confrontation between the government branches” because of the number of top executive branch officials listed as defendants. Grant said the case would also pit courts against the government.

The 9th Circuit judges on Monday questioned whether an extraordinary order was warranted, asking Grant to explain why the government could not challenge the case through the normal appeals process.

“If we set the precedent on this kind of case, there’s no logical boundary to it,” said Judge Marsha Berzon, adding that the appeals court would be flooded with hundreds of similar requests if they granted the government’s motion.

Grant argued the unique set of defendants merited immediate action.

Julia Olson, the lawyer representing the teenagers, called on the judges to deny the request and “allow these young people to present their evidence in court.”