The Supreme Court appeared closely divided on Monday as it weighed whether to revive President Barack Obama's plan to spare from deportation roughly 4 million undocumented immigrants, raising the possibility of a 4-4 deadlock that would block the program.

Based on questions asked during the 90-minute oral argument in a case that tests the limits of presidential powers, the court's four liberal justices seemed poised to back Obama while the four conservatives were more skeptical.

If the court is to avoid a 4-4 split, Chief Justice John Roberts could be the most likely member of the conservative bloc to join the liberals in voting to reinstate the program. One possible compromise outcome would be that the court could uphold Obama's plan while leaving some legal questions unresolved, including whether the government can provide work permits to eligible applicants.

The case, one of the biggest of the court's current term ending in June, pits Obama against 26 states led by Texas that filed suit to block his immigration plan.

If the court does muster a majority to decide the case, it appeared the justices would resolve the merits of the legal claim instead of deciding it on the narrow procedural question of whether the states had legitimate grounds to sue.

Texas said it had "standing" to sue because it would be hurt by the additional costs it would incur by providing driver's licenses to those who obtain legal status.

Justice Ruth Bader Ginsburg noted the "basic problem" is that the government does not have the resources to deport all of the estimated 11 million undocumented migrants and said,

"There are these people who are here to stay no matter what."

Obama's plan was tailored to let roughly 4 million people — those who have lived in the U.S. at least since 2010, have no criminal record and have children who are U.S. citizens or lawful permanent residents — get into a program that shields them from deportation and supplies work permits.

The court will decide the case by June and at a time when immigration has become a contentious issue in the U.S. presidential campaign.