• Like other US and western officials recently, Sir Jeremy Fleming did not suggest there had been any signs of suspicious activity.
• Speaking on Radio 4's Today programme, Sir Jeremy warned that any talk of nuclear weapons was "very dangerous".
There are no current signs that Russia is considering the use of nuclear weapons in the Ukraine war, the head of GCHQ has said.
Like other US and western officials recently, Sir Jeremy Fleming did not suggest there had been any signs of suspicious activity.
Speaking on Radio 4's Today programme, Sir Jeremy warned that any talk of nuclear weapons was "very dangerous".
GCHQ would hope to see "indicators" if Russia planned to use them, he said.
"Any talk of nuclear weapons is very dangerous and we need to be very careful of how we are talking about that.
"It's clear to me that whilst we might not like and in many ways abhor the ways the Russian military machine and President Putin are conducting this war, they are staying within the doctrine that we understand for their use, including for nuclear weapons."
He added: "I'm sure Putin's worried about the dangers of escalation. He thinks about those in different terms. But I think it is a sign that he has not reached for these other forms of waging war."
The comments come as the head of the intelligence agency plans to say in a speech on Tuesday that Ukraine is turning the tide against "exhausted" Russian forces.
He will say President Vladimir Putin's decision-making has proved "flawed".
"We know - and Russian commanders on the ground know - that their supplies and munitions are running out," Sir Jeremy will say in his speech at the annual Royal United Services Institute security lecture.
He will argue that the mobilisation of prisoners and inexperienced men "speaks of a desperate situation" - and will also directly criticise President Putin as isolated and making mistakes.
Speaking on Radio 4's Today programme about the state of the Russian military, Sir Jeremy said it was "running short of munitions" and "is certainly running short of friends".
"The word I have used is desperate," he said. "We can see that desperation at many levels inside Russian society and Russia's military machine."
But he warned that the missile attacks on targets across Ukraine on Monday showed Russia was still "very capable" of causing damage.
He added: "Russia's military machine can launch weapons, it has deep stocks and expertise. And yet, it is very broadly stretched in Ukraine."
The intelligence chief will also assert that the UK and its allies are at a defining moment when it comes to China.
The director of the intelligence, cyber and security agency will say the costs to Russia of the war in Ukraine - in terms of both people and equipment - are "staggering" as early gains are now reversed.
"With little effective internal challenge, his decision-making has proved flawed. It's a high stakes strategy that is leading to strategic errors in judgement."
Sir Jeremy also claims the Russian people are now starting to understand the problems caused by what he describes as Putin's "war of choice".
"They're seeing just how badly Putin has misjudged the situation," he will say.
"They're fleeing the draft, realising they can no longer travel. They know their access to modern technologies and external influences will be drastically restricted."
In a speech in March, Sir Jeremy said intelligence had showed some Russian soldiers in Ukraine had refused to carry out orders, sabotaged their own equipment and accidentally shot down one of their own aircraft.
The bulk of his lecture on Tuesday focuses on China. He will describe the UK as being at a "sliding doors moment" in which different paths taken will define the future.
He argues the Chinese Communist Party is aiming to manipulate the technology that underpins people's lives to embed its influence at home and abroad and provide opportunities for surveillance.
But the intelligence chief said he would not stop children using TikTok - which is owned by Chinese firm ByteDance - but said young people should be more aware of their personal data and how it could be shared.
"No, I wouldn't (stop children from using TikTok), but I would speak to my child about the way in which they think about their personal data on their device," he told BBC Radio 4's Today programme.
"I think it's really important from a very early age that we understand that there is no free good here. When we are using these services we are exchanging our data for that and if it's proportionate and we're happy with the way that data is safeguarded then that's great.
"Make the most of that, make those videos, use TikTok - but just think before you do," he added.
He will also warn that China is seeking to create "client economies and governments" by exporting technology to countries around the world, saying these countries risk "mortgaging the future" by buying in Chinese technology with "hidden costs".
He will say this includes areas like: new standards for the internet which could provide tracking methods and greater government control; Chinese digital currencies - which could be used to monitor the transactions of users and try to evade the type of sanctions imposed on Russia; and plans for a Chinese satellite system, citing fears it could be used to track individuals.
Chinese control of these areas is not inevitable, he will say, adding: "Our future strategic technology advantage rests on what we as a community do next."