European leaders, politicians and analysts got a jolt this week when United States President-elect Donald Trump, just days before his inauguration, criticised German Chancellor Angela Merkel and called Nato obsolete.
Growing uncertainty over Mr Trump's policies on Europe, Nato and Russia is coupled with concern over his apparent scepticism about intelligence briefings and open public sniping at the US' own intelligence agencies.
Friction between US intelligence agencies and presidents is not new but has never been played out so publicly. Developments are thus being watched with some alarm by analysts for the potentially corrosive effects of suspicion and distrust not just within the new administration, but also between the US and its allies.
Former House Intelligence Committee chairman Mike Rogers, a Republican, on Monday wrote on CNN: "While there will be friction and conflict, it is necessary that this takes place behind closed doors.
"On an international level, we should be... concerned about how this ongoing dispute appears to our partner intelligence services in Europe, Asia and the Middle East.
"If it appears that the president does not trust the quality and accuracy of CIA (Central Intelligence Agency) intelligence assessments, why should Britain's Secret Intelligence Service or Germany's Bundesnachrichtendienst?"
Worry is spreading in intelligence circles, analysts say.
Last week, an Israeli newspaper report claimed US intelligence officials had warned their Israeli counterparts to "be careful" when transferring intelligence to the White House after Mr Trump becomes president.
The issue is rooted in his open distrust of the intelligence community's assessment that Russia interfered in the November presidential election by selectively undermining his rival, Mrs Hillary Clinton, and tilting the scales in his favour. This has fed a sense of foreboding in the US intelligence community.
One analyst, who asked not to be named, told The Straits Times intelligence professionals across the political spectrum had "bad memories" of how assessments were manipulated in the run-up to the 2003 invasion of Iraq, and were "concerned about what to expect from Trump".
"A lot of the folks who have been seconded to the National Security Council from Defence, State and the intelligence community are trying to get out before Trump takes over," he said.
This risks dysfunction within and between security agencies at home and abroad, analysts say.
Outgoing CIA director John Brennan has already shot back at Mr Trump - in public.
On Sunday, Mr Brennan told Fox News: "There is no basis for Mr Trump to point fingers at the intelligence community for leaking information that was already available publicly."
The next day, in a last interview with the Wall Street Journal, he acknowledged the right of the US president to "challenge the conclusions of the intelligence community" . But he added: "It's when there are allegations made about leaking or about dishonesty or a lack of integrity, that's where I think the line is crossed."
Mr Blaise Misztal, director for national security at the Bipartisan Policy Centre in Washington, DC, told The Straits Times that the public feuding is risky "though it is too early to tell how big the risk is''.
"It is still plausible to believe at this point that Trump's reaction is against what he perceives is the politicisation of intelligence and the heads of the various intelligence agencies are acting on the political instructions of President Barack Obama. The test will come on Jan 20 and the days thereafter."
The CIA is to get a new director soon - Mr Mike Pompeo, an ultra conservative former congressman. Mr Trump plans an overhaul of the agency as well as the office of the Director of National Intelligence, seeing both as becoming politicised.
But Mr Misztal warned: "If he (Mr Trump) continues to publicly feud with the intelligence community, or if he has the same air of not really caring about intelligence briefings, then it will start to become corrosive."