Washington (CNN) Donald Trump is not even President yet, but he's already turning US foreign policy on two of the biggest challenges to American power -- China and Russia -- on its head.

In just five weeks as President-elect, Trump has given the world a taste of what Americans know already after a tumultuous political year: He is unpredictable, doesn't play by the usual rules and will chart an idiosyncratic course.

Nowhere is this clearer than the nascent Trump administration's evolving policy on Russia and China, which is emerging from on-the-fly comments, tweets from the President-elect himself, and a controversial potential pick for secretary of state.

Already, the President-elect appears to be bent on pulling off a full reversal of Obama administration policy towards one historic rival and a rising one.

After initially seeking to reset relations with Russia, President Barack Obama's team moved gradually to a position of hostility towards the Kremlin once Vladimir Putin returned to the presidency -- especially after his annexation of Crimea in 2014.

But Obama sought to manage the highly delicate relationship with China with as little confrontation as possible, using the protocol-heavy formulations that have endured for 40 years. The policy was tested by President Xi Jinping's increasingly assertive and nationalistic leadership style and Beijing's aggressive pursuit of territorial claims in the South and East China Seas. But it also resulted in Beijing and Washington agreeing to join the Paris climate accord.

Trump has deliberately escalated a showdown with China -- calling into question the bedrock principles that have governed US relations with Beijing. He appears ready to use the "One China" policy that has ensured no open conflict between the US and China over nationalist Taiwan as leverage.

"‎I fully understand the One China policy, but I don't know why we have to be bound by a One China policy unless we make a deal with China having to do with other things, including trade," Trump said on "Fox News Sunday."

As he hikes tensions with China, Trump is showing every sign of aligning American foreign policy closer to Moscow -- even at a time when Russia is threatening the post-World War II and post-Cold War settlement in Europe.

Trump named ExxonMobil CEO Rex Tillerson -- who considers Putin a friend, as secretary of state Tuesday. He has also talked of working with Russia in Syria to jointly combat ISIS, even though Moscow is allied with Syrian President Bashar al-Assad, who the Obama administration considers a war criminal after presiding over the vicious civil conflict that has torn his country apart.

Russia rift with US intelligence agencies

Trump has wide latitude to shift US foreign policy priorities and examine and change the certainties that have underpinned Washington's global posture for decades. But his approach to managing great power relations -- even before he takes the oath of office -- is a clear sign of the global turbulence that could lay ahead.

Trump's position on Russia especially, has led him into a stunning showdown with American intelligence agencies, suggesting a fraught relationship between the White House and top spies once Trump is in the Oval Office.

The President-elect has repeatedly stoked a public feud with the Central Intelligence Agency, rejecting the conclusions of US spies that Moscow is behind a massive hacking operation targeting the presidential election.

His position has also put him at odds with some senior Republicans vowing to join a bipartisan effort to investigate the cyber incursion.

In a highly unusual scenario, his comments appear to place the President-elect closer to the position of Moscow on the alleged hacking operation than the entire American intelligence community.

Trump dismissed a conclusion by the CIA, reported by The Washington Post, that Russia intervened in the election to help him win as "ridiculous" in his Fox interview.

Trump's transition team has also worked hard to make the issue a political one -- arguing that those who are disappointed by Trump's election victory are mounting an effort to tarnish his presidency.

"I think really clearly what this is is an attempt to try to delegitimize President-elect Trump's win," Trump spokesman Jason Miller told reporters on Monday. "That really seems to be what's going on here."

But Nicholas Burns, a former senior State Department official who supported Hillary Clinton in the presidential race warned that Russian election hacking represented a severe threat to US security and faulted Trump's response -- and questioned the wisdom of trying to improve relations with the Kremlin under the circumstances.

"If these allegations are true, this would be one of the most dangerous anti-American acts by a foreign power in a long time," Burns told CNN's "New Day" on Monday.

"I think that President Trump's reaction, which is to criticize the intelligence agencies and in a very weak way not Russia, I think that was inappropriate and unwise of him -- he has to lead these people."

The rising drama around the transition, suggests that Trump's personality, reaction to slights and tendency to punch back hard when attacked will be key features of his presidential leadership style.

Putting basis of relationship with China in play

The reaction from China and elsewhere to his statements meanwhile underlines the vast difference from being a candidate -- where a potential president's comments are often taken by foreign powers with a pinch of salt -- and being President-elect whose comments have a huge impact around the world.

The controversy erupted after Trump accepted a congratulatory call from Taiwanese President Tsai Ing-wen -- contravening precedent under which presidents and presidents-elect have declined contact with Taiwanese leaders.

China reacted angrily to the call, after a measured initial first reaction, but Trump told Fox that he would not accept being told what to do by Beijing.

"I don't want China dictating to me and this was a call put into me." he told Fox.

Trump's call with Tsai shocked many China watchers, but some observers in Washington suggested that it would not be a bad thing to put Beijing on notice that the relationship with Washington could not stay frozen in the past.

Trump appears to be putting the entire basis of the US-China relationship in play and seems willing to bring up an issue -- Taiwan -- which is of existential importance to Beijing.

Yet while he is challenging China, Trump is giving no real indication of the framework of policies that he hopes to put in the place of enduring foreign policy principles followed by the United States.

That is causing deep disquiet among US allies in Asia and among foreign policy experts in Washington.

"Sending signals that he intends to make major changes in US foreign, security, and economic policy is one thing," said Anthony Cordesman of the Center for Strategic and International Studies in a new commentary on Monday.

"Sending signals that undermine existing US policies without providing clear signals about the policies that will replace them is quite another."

But Trump's hyper-active transition and determination to make clear he is planning a departure on foreign policy suggest that 2017 could be a turbulent year in geopolitics.

"The campaign is over, and for all practical purposes, the presidency has begun," Cordesman wrote.