Washington (CNN) Donald Trump had a foreign policy sales pitch for U.S. voters and a blunt message for the world Wednesday: America comes first.

The Republican presidential front-runner proposed a sweeping redirection of America's global role in a major speech, part of a string of planned addresses designed to flesh out what a Trump administration would look like and to establish leadership credentials ahead of an increasingly probable general election clash with Democrat and former Secretary of State Hillary Clinton.

The billionaire businessman simultaneously addressed restive American voters and global elites worried by his fiery rhetoric on national security: He stressed that the United States would always put its economic and foreign policy interests first but said that allies in Europe, Asia and the Middle East would benefit from a much stronger, less ambiguous U.S. role in the world -- as long as they were prepared to pay up.

"America first will be the overriding theme of my administration," Trump said in his remarks at Washington's Mayflower hotel, delivered from a prepared text and in a subdued fashion starkly at odds with the free-wheeling rhetorical style that has powered his political rise on the campaign trail.

"Under a Trump administration, no American citizen will ever again feel that their needs come second to the citizens of foreign countries," Trump said.

He added, "My foreign policy will always put the interests of the American people and American security first."

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The speech appeared to be a multi-pronged attempt to reach out to a host of important constituencies.

First, he appealed to a Republican foreign policy establishment that has been highly critical at points of his credentials on global national security policy. Second, he tried to reach wavering Republicans who may be excited by his harsh critique of the "Obama-Clinton" foreign policy. And third, he sought an affirmation to loyal supporters who have flocked to his "Make America Great" slogan amid claims that the United States is weak and not respected by its enemies or foes. His remarks immediately elicited criticism from Democrats, but some GOP insiders offered positive words that have until now been in short supply for Trump.

He spoke the morning after a sweep of five primary states that drew him markedly closer to the delegate total needed to claim the Republican nomination and at a time when his campaign has begun a broad effort to cast him in a more presidential light.

But Trump often lacked specifics, delivering little in the way of a recognizable foreign strategy and repeating many of his campaign trail declarations, and did not explain in detail how his ideas would be implemented or touch on the likely response from American allies and enemies to his sharp reorientation of U.S. global principles.

In comments likely to cause shockwaves among U.S friends in Europe and Asia, Trump previewed early attempts to cut deals with Russia and China -- seen by many adversaries as bent on overthrowing the current security order guaranteed by America. If there was not a good deal to be had, Trump warned, he would be prepared to walk away.

But he also said he would not rush to war, striking an isolationist note that contrasts with the last Republican administration of George W. Bush.

However, Trump was introduced by Zalmay Khalilzad, President George W. Bush's former ambassador to Afghanistan, Iraq and the permanent representative to the United Nations.

"I will never send our finest into battle unless necessary, and I mean absolutely necessary, and will only do so if we have a plan for victory with a capital V," Trump emphasized.

Trump opened his speech vowing to "shake the rust off America's foreign policy" and said he would outline a vision for a U.S. foreign policy "that replaces randomness with purpose, ideology with strategy and chaos with peace."

The billionaire then tore into Obama's foreign policy, panning the Iran nuclear deal and claiming the President has "weakened our military by weakening our economy."

He sought to wrap Clinton in his criticism of the Obama administration as well, referring to the "legacy of the Obama-Clinton interventions" as one of "weakness, confusion and disarray."

At the same time, he offered an olive branch of sorts to Muslim allies of the United States in rare remarks pointing to the ways in which the U.S. can have constructive relations with the Muslim world.

"We're going to be working very closely with our friends in the Muslim world, which are all at risk for violent attacks," he said.

His comments on Muslims and Middle East partners have been lightning rods throughout the campaign.

Trump had previously called for a temporary ban on Muslim foreigners entering the United States and suggested that U.S. Middle East allies need to shoulder more of the cost of American military involvement in the region.

But he added that these countries also need to acknowledge America's contributions.

"This has to be a two-way street," he said. "They must also be good to us. It's no longer one way, it's two way."

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Trump also put America's allies elsewhere on notice that they, too, must start making a more tangible financial contribution. He said he would call summits in Europe and Asia to discuss "a rebalancing of commitments."

He previewed a substantial shift toward two of America's most important global rivals, China and Russia. He vowed to reverse China's "assault on America's jobs and wealth" and to use America's "economic power" over China to bring Beijing into line.

But he also pledged to fix relations with the rising Asian giant, saying that a stronger America would win more respect from its Communist leaders. But if that didn't work, Trump said he would be prepared to walk away, without offering specifics on the economic and national security consequences that would entail.

"We can both benefit or we can both go our separate ways. If need be, that's what's going to happen," he warned.

Retired Adm. Charles Kubic, a member of Trump's national security advisory committee, conceded Wednesday that many world leaders have been "shaken" by Trump's brash rhetoric and at-times radical policy positions.

"Sometimes it's hard when you believe a narrative for such a long time, and you have another narrative forced upon you. When somebody's saying, 'No, we're not going that direction,' it's very difficult to understand it," Kubic told CNN.

But Kubic said that while it might sound "harsh" at first when Trump "speaks the truth," it begins to make sense once you think about it more.

Reaction to Trump's speech from his political foes was swift and scathing.

Former Secretary of State Madeleine Albright, who supports Clinton, described his comments as a "simplistic" mixture of slogans and contradictions.

"He just underscored the fact that he is running the most reckless and dangerous presidential campaign in modern history," Albright said on a Clinton campaign conference call.

On the same call, Democratic Virginia Sen. Tim Kaine said that the last thing the world needed was an "unpredictable" United States, saying allies needed to know they could count on Washington and adversaries needed to understand there will consequences for acting against America.

Trump's main Republican rival, Texas Sen. Ted Cruz, said the speech showed that Trump "fails the presidential test" and pressured the billionaire to force any foreign policy advisers who have worked as lobbyists to declare their links to foreign governments.

But GOP Tennessee Sen. Bob Corker, who chairs the Senate Foreign Relations Committee, praised the speech.

"Today, Donald Trump delivered a very good foreign policy speech in which he laid out his vision for American engagement in the world," Corker said. "I look forward to hearing more details, but in a year where angry rhetoric has defined the presidential race on both sides of the aisle, it is my hope that candidates in both parties will begin focusing not only on the problems we face but on solutions."

And former Republican House Speaker Newt Gingrich tweeted that though elites would ridicule the speech, Trump had delivered a "serious" foreign policy address worth thinking and arguing about.

Trump later thanked Gingrich on Twitter for his tweets.

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Though Trump noted ahead of time that he wouldn't be outlining a "doctrine," he did criticize Obama for too often telegraphing its military moves in advance, thereby tipping off enemies, a practice he pledged to end.

"We have to be unpredictable. And we have to be unpredictable starting now," he said.

And he offered a glimpse into his political purpose, saying it was time to flush out ineffective establishment foreign policy operatives, striking a similar note to his themes on domestic issues.

"We have to look to new people because many of the old people frankly don't know what they're doing, even though they may look awfully good writing in the New York Times or being watched on television."

He closed by expanding on his trademark slogan: "We must make America respected again. We must make America truly wealthy again and we must, we have to and we will make America great again," he declared. "And if we do that, perhaps this century can be the most peaceful and prosperous the world has ever ever known."