Washington-The U.S. Supreme Court has dealt a severe blow to President Barack Obama after blocking his bid to shield millions of migrants from deportation.

Justices in the under-strength court were split 4-4 over Obama’s bid to change immigration policy by executive action, thus leaving lower court rulings blocking the effort in place.

Obama seemed to be angered by Thursday’s decision. He dubbed the ruling “heartbreaking for the millions of immigrants who made their lives here” but warned his opponents they will not be able to thwart their dreams for much longer.

“In November, Americans have to make a decision about what we care about and who we are,” he declared, in a nod to the White House race between Democrat Hillary Clinton and Republican Donald Trump.

Obama said the U.S. immigration system has been broken for two decades and that this ruling set it back even further.

The U.S. President had unveiled his plan in 2014.

The plan was tailored to let roughly 4 million people – those who have lived illegally in the United States 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 issue has been largely discussed during the presidential campaign.

In some of the toughest anti-immigrant rhetoric ever used by a major party candidate, Trump has vowed to build a wall along the Mexican border to keep out “rapists” and drug dealers.

He has also promised to suspend all immigration by Muslims and by people “from areas of the world where there is a proven history of terrorism against the United States, Europe or our allies.”