I have lauded Marco Rubio's view which declared that the short period of a unipolar world has come to an end.

The new Secretary of State had said:

"So it’s not normal for the world to simply have a unipolar power. That was not – that was an anomaly. It was a product of the end of the Cold War, but eventually you were going to reach back to a point where you had a multipolar world, multi-great powers in different parts of the planet."

If find that a much better concept than the 'rules based order'.

There are however different flavors of multipolarity.

The one Rubio likely thinks of is one in which might makes right. Several 'big dog' countries are sharing the globe, avoiding each other, while a number of small nations must do as they are told by whatever big power that can make them do so.

Witness the recent interactions between the U.S. and Colombia, Panama, Mexico and Canada. The Trump administration has threatened these countries with tariffs and other measures. After it had got what it wanted it pulled back at least a part of the threat (tariff). Unless it meets strong resistance it will repeat doing that again and again.

Another flavor of multi-polarity, one which Russia and China will likely support, is acknowledging that all countries, big or small, have equal rights. This is the base of the United Nations system which was born during allied talks in Yalta and Potsdam at the end of World War II.

Sergei Lavrov, the long term Foreign Minister of the Russian Federation, is arguing for upholding it:

The UN Charter Should Become the Legal Foundation of a Multipolar World – Global Affairs, Feb 4 2025

Eighty years ago, on 4 February 1945, the leaders of the victors of World War II―the Soviet Union, the United States, and Britain―opened the Yalta Conference to determine the contours of the postwar world. Despite ideological differences, they agreed to eradicate German Nazism and Japanese militarism. The agreements reached in Crimea were reaffirmed and elaborated upon at the Potsdam Conference in July-August 1945.

One result of the negotiations was the creation of the United Nations and the approval of the UN Charter, which to this day remains the main source of international law. The Charter set forth goals and principles for countries’ international behavior, which are designed to ensure their peaceful coexistence and sustained development. The principle of states’ sovereign equality laid the foundation for the Yalta-Potsdam system: none may claim dominance, as all are formally equal regardless of territory, population, military capabilities, or other metrics.
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It was at the UN that, with a key role played by the USSR, the foundation was laid for the multipolar world that is now emerging before our eyes.
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As Russian scholars rightly note, any international institution is, above all, “a way to limit the natural egoism of states.” The UN, with its consensus-adopted Charter, is no exception.

With this in mind Lavrov set out to criticize Marco Rubio's (and Donald Trump's) word-view. 

Lavrov is specifically aiming at Rubio's January 15 Opening Remarks Before the Senate Foreign Relations Committee. Rubio stated in these:

So while America too often prioritized the global order above our core national interest, other nations continued to act the way nations have always acted and always will: in what they perceive to be their best interest. And instead of folding into the post-Cold War global order, they have manipulated it to serve their interests at the expense of ours.
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The post-war global order is not just obsolete, it is now a weapon being used against us. And all this has led to a moment in which we must now confront the single greatest risk of geopolitical instability and of generational global crisis in the lifetime of anyone alive and in this room today. Eight decades later, we are once again called to create a free world out of the chaos, and this will not be easy. And it will be impossible without a strong and a confident America that engages in the world, putting our core national interests once again above all else.

Eight decades after the declaration of the UN Charter Rubio has set out to demolish it. He rejects the 'principle of states’ sovereign equality' and replaces it with an 'America First' and might makes right order.

Lavrov is warning, staunchly, that this will lead to chaos:

In 2025, with Donald Trump’s Republican administration back in power, Washington’s interpretation of international processes since World War II has taken on a new dimension, as vividly described to the Senate by new Secretary of State Marco Rubio on 15 January: not only is the postwar world order outdated, but it has been turned into a weapon against U.S. interests. In other words, not only the Yalta-Potsdam order is undesirable; so, too, is the ‘rules-based order’ that had seemed to embody the selfishness and arrogance of the U.S.-led West after the Cold War. “America first” is alarmingly similar to the Hitlerite slogan “Germany above all”, and a wager on “peace through strength” may be the final blow to diplomacy. Not to mention that such statements and ideological constructs show not even the slightest bit of respect for Washington’s international legal obligations under the UN Charter.
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Brazen attempts to reorder the world in one’s own interest, violating UN principles, may beget instability, confrontation, and even catastrophe. Given the current level of international strife, recklessly rejecting the Yalta-Potsdam system, with the UN and UN Charter at its core, will inevitably lead to chaos.

(A few years ago the German 'above all' slogan was copied by the U.S. Air Force but later pulled back.)

China has a more guarded but similar take. A recent op-ed in a Spanish language newspaper by the Chinese Ambassador to Panama has been taken up as the lead headline in China's Global Times:

Chinese ambassador to Panama calls on US to 'learn to respect' as Rubio visits the country to exert pressure – Global Times, Feb 04 2025

Xu's article came as US Secretary of State Marco Rubio visited Panama in his first trip abroad since taking office. Rubio aimed to exert pressure on the country concerning its relations with China.

Xu wrote that while chanting "Make America Great Again," the US delegation's visit to Panama caused a stir greater than a tropical storm.
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In the international community, all countries are equal and have the right to independently develop diplomatic relations. No one has the right to dictate to others or issue commands. If the US wants to create the golden age of the Americas, it must first respect other countries and listen to Latin American nations about their vision for the future, Xu wrote.

The Trump administration's version of multipolarity is incompatible with the one China and Russia have in mind. It contradicts the UN Charter.

If that does not change we will be in for a big clash.

/Sidenote:/

Under pressure from Rubio Panama declared that it would not renew its participation in China's Belt and Road Initiative (BRI). This was lauded as Rubio's victory.

However there were only three BRI projects ever in Panama:

Panama is contracting with Chinese companies for a fourth bridge over the Panama Canal, as well as a third line for the Panama City mass transit system.

China has also submitted a $4.1 billion proposal to build a 391-kilometer (243-mile) high-speed rail line from Panama City to the town of David near its border with Costa Rica — a project to be carried out under the rubric of the Belt and Road.

After some planing hustle the fourth bridge over the Panama Canal is finally being build. The third line for Panama city was and is however a Japanese project. The high-speed rail line from Panama City to David is not economically feasible. Five years after the initial plans its construction has not even started. It is unlikely to ever being build.

Neither Panama, nor China, will thus lose anything from Panama's BRI retreat.

Rubio's 'victory' in Panama was pure propaganda.

/End sidenote/