Washington (CNN) Pennsylvania Republicans are asking the US Supreme Court to block new congressional maps that would tilt several key races in Democrats' favor from being used in this year's midterm elections.

The GOP leaders of the state House and Senate asked Tuesday for an emergency stay blocking the implementation of the maps, which were unveiled this month by the state Supreme Court after it ruled that the previous maps had been gerrymandered in violation of Pennsylvania's Constitution.

It's a final effort to stop major changes to a congressional delegation that now comprises 13 Republican-held seats and five Democrats.

Lawyers for House Speaker Mike Turzai and Senate President Pro Tempore Joseph Scarnati argue that the state's high court overstepped its authority in setting a deadline for lawmakers to draw new maps -- and then, when the GOP-led Legislature missed that deadline, producing new maps on its own.

In court papers, their lawyers said the state court's move "blatantly usurps the power of the Pennsylvania General Assembly and inflicts confusion on the Commonwealth's upcoming congressional elections."

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