WASHINGTON - Donald Trump's plan to ban Muslims from entering the United States is shoving the Republican Party to the edge of chaos, abruptly pitting GOP leaders against their own presidential front-runner and jeopardizing the party's longtime drive to attract minorities.

Unbowed, Trump fired a searing warning Tuesday via Twitter to fellow Republicans carping about his proposal. A majority of his supporters, he tweeted, "would vote for me if I departed the GOP & ran as an independent."

The cross fire between Trump and frustrated Republicans became a furious blur the day after the billionaire businessman announced his plan.

Beleaguered 2016 rivals condemned his proposal and complained that his divisive positions were dominating attention in the crowded Republican contest. Party elders, meanwhile, warned that too much criticism might indeed push him to abandon the GOP and launch a third-party bid that could hand the presidential election to the Democrats.

And Republicans up for reelection in the Senate grew terse in the Capitol hallways as they were asked again and again to respond to Trump's remarks - a glimpse of their political futures if the former reality-show star captures the GOP nomination.

"This is not conservatism," declared House Speaker Paul Ryan, the Republican Party's top elected leader. "What was proposed yesterday is not what this party stands for. And more importantly, it's not what this country stands for."

In Philadelphia, Mayor Nutter snatched up the welcome mat, saying he wished he could ban Trump from the city.

"Certainly if I had the power to do so, the only banning that should be done is that of that person not being allowed in the city of Philadelphia," Nutter said Tuesday. "We have no place for that kind of ignorance and intolerance and lack of understanding of what our country is about."

The mayor, a Democrat, addressed Trump's remarks during an unrelated City Hall news conference. "Unfortunately, many are playing a political game for their own gain, which undermines the fundamental values of what the United States of America is all about," Nutter said, referring to Trump's remarks.

One by one, Republican officials across the country lashed out at Trump's plan, announced the night before, which calls for a "total and complete shutdown of Muslims entering the United States" to help quell the threat of terrorism.

But party leaders are well aware of the possibility that he could end up running against the GOP nominee next year if it's not him, a threat they have long feared.

The Republican Party, said Jeb Bush adviser Ana Navarro, is stuck between "a rock and a jerk" less than eight weeks before the first votes are cast in Iowa.

Tom Ridge, a former Republican governor of Pennsylvania who became the first secretary of the Department of Homeland Security, said Tuesday he would not vote for Trump. Ridge said that his anger over Trump's popularity has been building for months and that he was frustrated that many fellow Republicans took so long to denounce the candidate's rhetoric.

"I think the man is an embarrassment to my party," said Ridge, who supports Trump rival Jeb Bush. "He's an embarrassment to our country. We deserve better than this."

In Mississippi, RNC member Henry Barbour said Trump's comments "aren't worthy of someone who wants to occupy 1600 Pennsylvania Avenue." He said Trump would be a "disaster politically for the GOP if he won the nomination."

"It's embarrassing at best," Barbour said of Trump's impact on his party.

Barbour helped write the Republican National Committee's "Growth and Opportunity Project" after a painful 2012 presidential election that forced party leaders to reevaluate their strategy in presidential contests to reflect the nation's demographic shifts. Among other things, the report cited an urgent need for GOP leaders to adopt an inclusive and welcoming tone on issues such as immigration.

"If we want ethnic minority voters to support Republicans, we have to engage them and show our sincerity," it read, noting that white voters made up a record-low 72 percent of the electorate in 2012 and would represent less than half of all voters by 2050.

Yet Trump has vaulted to the top of the Republican 2016 field by attacking immigrants in many cases.

He called some Mexican immigrants "rapists" and "criminals" in his announcement speech and intensified his criticism of Muslim immigrants or visitors Monday evening. While experts widely consider his proposal unconstitutional, Trump's continued popularity underscores the deep divide between Republican leaders and the party's conservative base, which holds outsized influence in the presidential nomination process.

Indeed, Trump's plan was cheered during a South Carolina rally Monday evening, and vocal supporters across the country defended the Muslim ban as necessary for national security. Polling suggests the sentiment is likely fueled by a sharp strain of xenophobia: A new AP-GfK poll found 8 in 10 Republicans think there are too many immigrants coming from the Middle East.

Trump showed little concern for critics on Tuesday. "I don't care about them," he told CNN. "I'm doing what's right."

The debate over Trump's plan left his Republican presidential competitors struggling for attention with little time remaining before Iowa's Feb. 1 caucuses.

Speaking on The Michael Medved Show, Gov. Christie called Trump's idea "ridiculous" and denounced it as "the kind of thing that people say when they have no experience and don't know what they're talking about." He added, "We do not need to endorse that type of activity, nor should we."

Inquirer staff writer Claudia Vargas contributed to this article. It also contains information from the Washington Post.