Trump's 'sanctuary cities' plan not first choice, but an 'option on the table': Sarah Sanders Sanders said they don't want the burden to be "on one or two border cities."

White House press secretary Sarah Sanders said Sunday the potential plan to transfer undocumented immigrants from border cities to "sanctuary cities" is "an option on the table," though it's not the administration's first choice.

"We've talked about a number of different things over the last two years that we'd love to see happen. Certainly this wouldn't be our first choice because ideally we wouldn't be dealing with a massive influx of illegal immigrants coming across the border," Sanders said on "This Week."

"We don't want to put all of the burden on one or two border communities," she told ABC News Chief Anchor George Stephanopoulos. "Democrats have stated time and time again, they support open borders, they support sanctuary cities, so let's spread out some of that burden and let's put it in some of those other locations if that's what they want to see happen and are refusing to actually help fix the problem."

Trump tweeted Saturday about the plan, claiming, without citing any evidence, that the federal government “has the absolute legal right” to transfer undocumented immigrants into “sanctuary cities” after they legally have to be released from detention.

So-called sanctuary cities -- San Francisco, Chicago and New York are among those informally considered as such -- do not cooperate with the federal government in complying with Immigration and Customs Enforcement (ICE) requests.

The Washington Post broke the story about the plan on Thursday, which ABC News later confirmed, reporting it had been considered twice in the past six months.

However, while a White House official had told ABC News that the plan “was just a suggestion that was floated and rejected,” the president contradicted that on Friday, tweeting that there was in fact a plan still being considered to transfer undocumented immigrants to “sanctuary cities.”

“The Radical Left always seems to have an Open Borders, Open Arms policy – so this should make them very happy!” he tweeted, later in the day singling out California at an event discussing 5G technology. “They're always saying they have open arms, let's see if they have open arms.”

Senior-level sources familiar with the matter told ABC News that the proposal was aimed, in part, to punish political rivals by placing immigrants in their districts.

A senior official at the Department of Homeland Security told ABC News that Trump himself raised the issue directly with then-Secretary Kirstjen Nielsen, who submitted her resignation April 7.

Nielsen asked the legal team to review the idea and they flatly rejected it, saying it is illegal, the official said.

“How can you continue to push this?” Stephanopoulos asked Sanders on “This Week.”

“Well, we’re looking to see if there are options that make it possible and doing a full and thorough and extensive review,” she said. “The president likes the idea and Democrats have said they want these individuals into their communities so let’s see if it works and everybody gets a win out of it."

But she added that this plan isn’t “the ideal situation.”

“The ideal solution is simple; it’s for Congress, particularly Democrats in Congress, to sit down with the president, do their jobs, and help us stop this awful crisis that’s taking place at our border,” Sanders said. “Again, that's not our first choice, probably not even our second or third choice, but we have to look at all options as long as Democrats refuse to do their jobs and fix the problem.”

Stephanopoulos also asked about a CNN report that said while in Calexico, California, earlier in April, Trump urged then Customs and Border Protection Commissioner and now acting DHS Secretary Kevin McAleenan to close the border and direct agents to refuse entry to asylum seekers. Under U.S. law, any individual who steps foot on American soil can claim asylum and that claim must be processed.

In its reporting, CNN noted it was unclear if the comment was a joke.

“Homeland Security pushed back on this, as has the president,” Sanders told Stephanopoulos.

“We're a country of laws and we have a president who supports that and is not asking anybody to do anything outside of those bounds. In fact, he's asking Congress to step up and give greater legal standing so they can do more to stop this crisis. No one’s trying to skirt the law and certainly not being encouraged by the president to do so,” she said.