The Black Lives Matter movement is creating an environment that can put police officers at risk, Republican presidential candidate Chris Christie said Sunday, accusing President Barack Obama of supporting the movement, encouraging "lawlessness" and not backing up law enforcement.

"I don't believe that that movement should be justified when they are calling for the murder of police officers," Christie said on CBS's Face the Nation. When challenged that individuals may have called for the deaths of officers, but not the official movement, Christie replied that the deadly environment is "what the movement is creating."

"The problem is this, there's lawlessness in this country, [and] the president encourages this," said Christie. When asked how Obama was encouraging lawlessness, the New Jersey governor said by his rhetoric and the fact he doesn't support the police.

Black Lives Matter was established after the 2012 shooting of Trayvon Martin, an unarmed teen, by a neighbourhood watch enthusiast, but gained widespread national attention two years later after the officer-involved deaths of Eric Garner in New York and Michael Brown in Ferguson, Mo.

The movement and slogan have become an issue in the 2016 presidential campaign. The group said on its Facebook page in September that conservatives are trying to turn the movement into a danger to officers.

"We're targeting the brutal system of policing, not individual police," the movement said in its statement. "The Black Lives Matter Network seeks to end the system of policing that allows for unchecked violence against black people."

Police groups have bristled at that comment and pointed out people in marches drawing awareness to the issue have been recorded chanting for the deaths of police officers. During a protest outside Minnesota's state fair this summer, for example, some marchers were recorded chanting to fry police "like bacon." Earlier this month, the parents of slain black men and women were featured speakers at the "Justice or Else" march marking the 20-year anniversary of the Million Man March in Washington.

Obama last week defended the Black Lives Matter movement, noting protests are giving voice to a problem happening only in African-American communities.

"We, as a society, particularly given our history, have to take this seriously," Obama said.

The movement has become an issue in the presidential campaign. Some have taken its name as an implication that other people's lives don't matter, and respond by saying, "All lives matter."

Democratic presidential hopeful Martin O'Malley initially took that tack but apologized last summer. At the Democratic presidential debate earlier this month, he joined the party's other presidential hopefuls in giving a nod to the movement. African-Americans overwhelmingly vote for Democrats.

"Black lives matter, and we have a lot of work to do to reform our criminal justice system, and to address race relations in our country," O'Malley said.

The FBI released preliminary figures earlier this year indicating that 51 law enforcement officers were feloniously killed in the line of duty in 2014, up from 27 officers killed in 2013. The 2013 total was the lowest recorded in the previous 35 years of data, with the final 2012 figure of felonious deaths pegged at 48, down from a 2011 total of 72 police officer deaths from felonious acts.

The non-profit Officer Down Memorial Page have recorded data so far this year that indicate 31 police officers in the U.S. were killed by gunfire, three from assault, three from vehicular assault, and four while involved in a vehicle pursuit.