BELFAST, Northern Ireland - Police were granted an extra 48 hours Friday to interrogate Sinn Fein leader Gerry Adams about the 1972 IRA killing of a Belfast widow, infuriating his Irish nationalist party and raising questions about the stability of the province's Catholic-Protestant government.

The Police Service of Northern Ireland confirmed in a statement its detectives received permission at a closed-door hearing with a judge to detain Adams for up to two more days.

Had the request been refused, authorities would have been required to charge Adams or release him Friday night, two days after his arrest in the abduction, slaying and secret burial of Jean McConville, a mother of 10.

The new deadline is Sunday night, although this too could be extended with judicial permission.

The unexpectedly long detention of Adams left senior party colleagues seething. Sinn Fein warned it could end its support for law and order in Northern Ireland - a key peacemaking commitment that enabled the creation of a unity government seven years ago - if Adams is charged.

Deputy First Minister Martin McGuinness, the Sinn Fein official who governs Northern Ireland alongside British Protestant politicians, said his party would reconsider its 2007 vote to recognize the legitimacy of Northern Ireland's police if Adams isn't freed without charge. Protestants required that commitment before agreeing to cooperate with Sinn Fein.

McGuinness, who like Adams reputedly was an Irish Republican Army commander for three decades, said Sinn Fein would "continue to support the reformers within policing" if Adams is freed.

"Or the situation will not work out in the way we believe that it should. If it doesn't, we will have to review that situation," he said.

Moderate politicians criticized Sinn Fein for making unreasonable threats.

Adams, who as Sinn Fein chief since 1983 is Europe's longest-serving party leader, denies any role in the IRA.