[WASHINGTON] Barack Obama's efforts to shield millions of illegal immigrants from deportation suffered a major setback at the US Supreme Court on Thursday - one the president said was "heartbreaking" for those affected.
Justices in the under-strength court were split 4-4 over Mr Obama's bid to change immigration policy by executive action, thus leaving lower court rulings blocking the effort in place.
The court normally has nine members, but Justice Antonin Scalia died in February and the Senate has refused to vote on Mr Obama's nominee to replace him.
The deadlock leaves Mr Obama's immigration policy in limbo, like the four million undocumented immigrants who stood to be awarded US work permits under the politically controversial plan.
"The fact that the Supreme Court wasn't able to issue a decision today doesn't just set the system back further - it takes us further from the country that we aspire to be," Mr Obama said shortly after the ruling was issued.
"I think it is heartbreaking for the millions of immigrants who made their lives here, who raise families here and hope for the opportunity to work, pay taxes, serve in our military and more fully contribute to this country we all love in an open way."
His fellow Democrats also were quick to express dismay.
"Yet another example of Scotus not being able to function as final word on a crucial constitutional issue," tweeted Senator Patrick Leahy, chiding Republican colleagues for blocking the appointment of a new justice.
"Do your job," he demanded.
Congressman Xavier Becerra declared: "As a nation built by immigrants, America must fight to keep families together, not tear them apart."
Republicans, however, celebrated what they saw as a victory for efforts to stop Mr Obama exceeding his executive authority to bypass Congress and force through controversial measures.
"Obama's illegal action on immigration has been blocked! A huge win for our Constitution and for our rule of law," tweeted Congressman Tom Marino, echoing the views of many of his colleagues.
Frustrated by Congress's repeated failure to pass immigration reform, in November 2014, Mr Obama issued a decree to allow migrants whose children are legally resident to apply for permits.
This would have shielded the families from deportation while the politically-charged issue of their status is determined, but the governors of 26 Republican-led states challenged the order.
Federal courts in Texas and Louisiana put the measure on hold and the case passed to the Supreme Court, which on Thursday remained split along progressive-conservative lines.
The decision - or non-decision - also thrusts the issue to the front and centre of what had already been the heated campaign for the November presidential election.
Republican White House hopeful Donald Trump has adopted some of the most hardline anti-immigrant rhetoric ever used by a major party candidate, vowing to build a wall along the Mexican border.
He has also vowed to suspend all immigration by Muslims and people "from areas of the world where there is a proven history of terrorism against the United States, Europe or our allies."
Mr Trump's Democratic rival, Hillary Clinton, has by contrast vowed "to create a pathway to citizenship, keep families together, and enable millions of workers to come out of the shadows."