The foreign secretary warned that the Ukraine-Russia peace talks could be used as a “smokescreen” for the Kremlin to regroup troops for a new offensive.
Liz Truss said it was up to President Volodymyr Zelensky how his country would approach the peace talks.
But in an interview with The Times, he said he feared the negotiations, which are said to have progressed, were a “smokescreen”.
Prime Minister Boris Johnson told the Scottish Conservative conference in Aberdeen that he had pledged to send more defensive weapons to Ukraine after speaking with Zelensky on Friday.
He said he was “more convinced than ever” that Russian President Vladimir Putin’s military enterprise would fail.
Johnson will address the Conservative Spring Forum in Blackpool on Saturday, where he is likely to address the conflict in Ukraine again.
Britain’s defense intelligence chief said Putin was now waging a “war of attrition” after initial expectations of a quick conflict faded.
Lt. Gen. Sir Jim Hockenhull said the Kremlin has been forced to change tactics, resorting to “reckless and indiscriminate” use of firepower that will inevitably lead to more civilian casualties.
Truss said that if Moscow was serious about holding peace talks with Ukraine, it would not use such methods.
She told The Times: “If a country is serious about negotiations, it doesn’t indiscriminately bomb civilians on that day.”
Truss said she was “very skeptical” about the talks the two countries were having, adding: “What we have seen is an attempt to create a space for the Russians to regroup.”
She said: “We do not see any serious withdrawal of Russian troops or any serious proposal on the table.”
The minister told the newspaper that “the Russians have songs, songs and songs. I am afraid that the negotiation is another attempt to create a distraction and create a smokescreen.”
But she said: “Of course, Ukraine, as a sovereign nation, has the full right to undertake any negotiation process it deems appropriate.”
Western officials have warned that the Russians have “enormous” stockpiles of artillery ammunition, meaning they could keep up their bombardment for weeks.
However, General Hockenhull said that after more than three weeks of campaigning, it is clear that the Kremlin has not yet achieved any of its initial goals.
“He has been shocked by the scale and ferocity of the Ukrainian resistance and has been beset by problems of his own making,” he told reporters.
“Russian operations have changed. Russia is now following a strategy of attrition. This will involve reckless and indiscriminate use of firepower.
“This will result in increased civilian casualties, the disruption of Ukrainian infrastructure and the intensification of the humanitarian crisis.”
Ms Truss told The Times: “What we have seen is an attempt to create a space for the Russians to regroup. Their invasion is not going to be planned.”
Johnson said now was the time to “tighten the screw” in Moscow.
“I am more convinced than ever that Putin will fail,” he said.
He will fail, because in his catastrophic adventure in the Ukraine he fatally underestimated the heroism and determination of the Ukrainians to fight.
“He underestimated the western unity.
“And among other things, by the way, he underestimated the passionate commitment of the people of this country to help.”
Earlier, Health Secretary Sajid Javid said the prime minister was being hailed as a hero in Ukraine.
Speaking at the Conservative Spring Forum in Blackpool, Javid said the support offered by the UK had “prompted a British Ukrainian, who stopped me in my constituency at almost exactly this time last week, and told me ‘next Whenever you see Boris, tell him that in Ukraine he is a hero.
Elsewhere in the conference, Education Secretary Nadhim Zahawi said 100,000 school places had been created for children fleeing Ukraine and virtual lessons created during the coronavirus pandemic had been translated into Ukrainian.
Leveling Up Secretary Michael Gove confirmed that more than 150,000 homes have been offered to house Ukrainian refugees, most of whom have arrived in Poland.
Former Prime Minister David Cameron announced Friday that he was driving a “small truck” to Poland’s border with Ukraine with supplies.
It comes as Putin, Russia’s president, made a rare public appearance to address a mass flag rally at Moscow’s Luzhniki stadium to mark the eighth anniversary of his country’s annexation of Crimea.
He praised the efforts of the Russian forces, stating: “Shoulder to shoulder, they help and support each other.”
So far, 7,000 Russian soldiers have been killed in the fighting, including four major generals and several other senior officers, US sources estimate.
In its latest intelligence update, the Defense Ministry said Russia was forced to switch to an “attrition strategy”.