United States president-elect Donald Trump's own Republican party is divided over how to respond to new reports Russian hackers may have helped him win the election.
Mr Trump has downplayed reports that the CIA believes hackers linked to the Russian government are responsible, calling the reports "ridiculous."
But several senators, including former presidential nominee John McCain among at least five leading Republicans, are calling for a congressional investigation.
And, now, Senate Majority Leader Mitch McConnell has become the most powerful Republican to back their cause.
"Any foreign breach of our cyber security measures is disturbing, and I strongly condemn any such efforts. This simply cannot be a partisan issue. The Russians are not our friends. They invaded Crimea. Senator McCain and I, and some of our Democratic friends, met with a delegation from the Baltic countries just this past week. To say that they are nervous about the Russians is to put it mildly. I think we ought to approach all of these issues on the assumption that the Russians do not wish us well."
It is the strongest sign yet that the Republican caucus will be willing to take stands against Mr Trump once he takes office next month.
The White House is also backing a congressional review, with spokesman Josh Earnest confirming intelligence agencies have been working closely with politicians from both parties.
He says the hacks clearly focused on the Democratic National Committee, not its Republican counterpart.
"You didn't need a security clearance to figure out who benefited from malicious Russian cyber activity. The President-Elect didn't call it into question. He called on Russia to hack his opponent. He called on Russia to attack Secretary (Hillary) Clinton. So he certainly had a pretty good sense of whose side this activity was coming down on. The last several weeks of the election were focused on a discussion of e-mails that had been hacked and leaked by the Russians. These were e-mails from the DNC and John Podesta, not from the RNC and Steve Bannon."
Mr Trump also remains under fire for his brief but historically significant telephone call with the president of Taiwan.
It has sparked an official complaint from China, which claims the call breaches almost 40 years of diplomatic protocol surrounding the so-called One China policy.
In 1949, the Chinese Communists forced the ruling government to flee to Taiwan.
While the Communists declared themselves the new government, the United States and most Western countries recognised the exiled government as legitimate.
But in 1979, the United States established formal diplomatic relations with China and agreed to acknowledge there was "one China and Taiwan is part of China."
Mr Trump insists, while he understands the policy, he will not be told who he can and cannot speak to.
Chinese foreign-ministry spokesman Geng Shuang says that could prove problematic to US-Chinese relations.
"The Taiwan issue has a bearing on China's sovereignty and territorial integrity and is related to China's core interest. We urge the new US administration and its leader to fully recognise the sensitivity of the Taiwan issue, stick to the One China policy, so as not to gravely disrupt or damage the general picture of the bilateral relationship."
An editorial in China's state-run Global Times newspaper was less diplomatic, calling Mr Trump "as ignorant as a child" when it comes to foreign relations.
World leaders, including German chancellor Angela Merkel, have quickly distanced themselves when asked if Mr Trump was right to question the long-held policy on Taiwan.
"We still stand by a One China policy, and we will not change our stance."
But global relations analysts such as Peter Jennings, from the Australian Strategic Research Policy Institute, say they see merit in Mr Trump's defiance.
"It may curb some Chinese adventurism in the South China Sea and elsewhere as they work out how they're going to manage their relationship with a new and very different president in Washington."
Meanwhile, shares in the US aircraft manufacturer Lockheed Martin have fallen over 5 per cent after Mr Trump criticised the company's F-35 fighter jet program.
He posted on Twitter that the program's costs were "out of control" and billions of dollars could be saved on military and other purchases once he is inaugurated.
Jeff Babione, from Lockheed's F-35 program, has defended the costs, saying the plane's price has already dropped more than 70 per cent.
"When we get to $85 million, the F35 will be less expensive than any fourth-generation fighter in the world and you'll have the premier fifth-generation fighter, and so that's an incredible value for anyone operating the airplane."
Since its inception, the F-35 program has been dogged by problems and costly retrofits.
Australia is one of six countries currently flying the jets.
