(CNN) – Republican Sen. Marco Rubio, speaking in London at the leading think-thank the Chatham House, said Tuesday America's changing demographics won't affect the country's longtime relationship with the United Kingdom, pushing back at the notion that the U.S.- U.K. bond solely relies on its ancestral ties.
In a speech about foreign policy, the potential presidential candidate also said he was skeptical of the initial nuclear deal reached for Iran. He also focused a significant portion of his remarks on posing threats by the Russian government, even taking a sharp attack on its President, Vladimir Putin.
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The first-term Senator from Florida praised the transatlantic alliance between the U.S. and the U.K., saying the partnership is still the leading force in the world and cautioned against letting that relationship slip.
"If we do not stand together for liberty and freedom, and instead allow our historic partnership to fade into history, an enormous vacuum will open up, and imagine the forces of darkness and evil that would gladly move in to fill the void," he said.
He added there will always be critics who argue the two nations have "had their days in the sun" and another world power will lead the way.
"But (those critics) underestimate the power of our nations, the power of our shared values," he said. "They underestimate what we have and can achieve together. More importantly they underestimate the will and moral courage of free men and women."
Asked whether America's increasingly diverse population could splinter the country's allegiance to Europe, Rubio said he doesn't "view that as problematic in any way."
"It's an exaggeration to say that somehow what binds our two nations and two societies together is the fact that people who live in the U.S., their relatives once came from the United Kingdom," he said, adding it's been "a long time since we've had mass migration from" that part of the world.
Rather, he argued, what binds them together is a common culture. As an example, he pointed to his daughters of Cuban descent who woke up early to watch the 2011 royal wedding and then stayed up late earlier this year to hear the announcement of whether the so-called royal baby would be a boy or girl.
And as he was getting ready for the London trip, he added, the most common question he got was whether he would meet a member of the world-famous boy band One Direction.
"I told them that I would not but that I would send them my regards," he said, laughing.
Rubio said those examples "may appear as trivial things" but it "really creates a connection between our two countries that is very real at the people-to-people level."
Iran, Russia and China as rising threats
Weighing in on the interim deal reached last month with Iran to slow its nuclear development, Rubio said he was "personally skeptical" of the agreement, saying Iran's "ultimate goal" for the negotiations is simply to get relief from sanctions, "while retaining the option of developing a nuclear weapon."
He added Iran "does not have a right to enrich" and warned of a potential arms race in the Middle East should Iran develop a nuclear weapon.
Rubio also spent a large part of his speech on the progress made since the Cold War, but argued countries on the eastern edge of Europe are still in danger from Russia's power grip.
The Senator argued the U.S. and the U.K. need to be "blunt about our differences with Vladimir Putin-differences with his government, not differences with his people." He argued Russia pressured Ukraine against a landmark trade deal with the European Union.
The transatlantic alliance also involves "reassuring allies in the region that we support their ambitions to move forward toward liberty, rather than backwards toward the days of Soviet domination."
His trip to London comes a couple of weeks after he delivered a major speech on international affairs in Washington, D.C., seen by many as attempt to boost his foreign policy chops should he decide to run for president in 2016.
Rubio also commented Tuesday on the controversy over China's newly-declared air defense zone over the East China Sea.
"This recent action by Beijing is an example of an issue in which it would be ideal to have America and Europe in lockstep, making clear to Beijing that freedom of flight in the region should not be held hostage to political agendas," he said.