In her first speech on the world stage as prime minister, Ms Truss will accuse the Russian president of “swords” after warning that his country will use “every means at our disposal” to protect itself. The comments appeared to suggest that the conflict in Ukraine could escalate into a nuclear crisis. Ukraine’s latest war: Putin’s mobilization order sparks fury Ms Truss will say Putin is “desperately trying to justify his disastrous failures” as she addressed the United Nations General Assembly (UNGA) in New York. “It doubles down by sending even more reservists to a terrible fate,” he will say. “It is desperately trying to claim the mantle of democracy for a regime without human rights or freedoms. “And it makes even more false claims and scary threats.” Ms Truss will praise the “power of collective purpose” in response to Mr Putin’s invasion so far, but warned that aid to Ukraine should not be reduced. And he will tell other world leaders that the UK will spend 3% of GDP on defense by 2030, repeating a promise he made when he campaigned to become Tory leader. He will add: “In the face of increasing aggression, we have shown that we have the power to act and the determination to end it. But this shouldn’t be a one-off. “This must be a new era in which we commit to ourselves, to our citizens and to this institution that we will do whatever it takes – whatever it takes to deliver for our people and defend our values.” The speech comes amid protests in Moscow after Mr Putin announced a partial military mobilisation, with 300,000 reservists to be called up. It brought people to the streets with more than 1,000 arrests by Wednesday evening, according to a rights group. Use Chrome browser for more accessible video player 3:15 WARNING: Flash photography from the start. Sky’s Diana Magnay reports from Moscow where protesters are being arrested. The Kremlin is trying to regain ground in the face of a counterattack by Ukrainian forces. In a televised address to the nation, Putin said it was “no bluff” when he pledged that Russia would use its weapons of mass destruction if its territory was threatened. The Russian leader accused the West of “nuclear blackmail” and claimed that “high-ranking representatives of leading NATO states” had talked about the possibility of using weapons of mass destruction against Russia. “To those who allow themselves such statements about Russia, I want to remind you that our country also has various means of destruction,” Mr. Putin said. Nuclear threats ‘taken very seriously’ The comments prompted strong responses from other world leaders, with Joe Biden using his address to the UN General Assembly to accuse Russia of violating basic principles of the UN Charter with its “brutal, unnecessary war” in Ukraine . A diplomatic source said the nuclear threat was “very real” and was being taken “very seriously” by officials. But they added: “We are not going to engage in a war of words over a nuclear threat from a man who postponed his speech last night, was shaking when he delivered it and is now trying to mobilize reservists who are trying to get to airports across Russia. His lies catch him.” Use Chrome browser for more accessible video player 2:39 Retired Air Vice Marshal Sean Bell explains what Vladimir Putin said about Russia’s weapons in his speech. Ms Truss is using her visit to the United Nations to rally support for Ukraine. However, it has not been able to escape the thorny issue of the Northern Ireland protocol. He discussed the issue in meetings with Mr Biden and Ursula von der Leyen on Wednesday. The prime minister is understood to be keen to break the deadlock over the protocol within the next six months, amid escalating tensions evident on her trip. Read more: Why Putin’s war escalation could give him a pretext to resort to nuclear attack Five British POWs held by Russia released While there has been no major progress in Northern Ireland since the meetings, the prospect of a state visit by the president to the UK to coincide with the 25th anniversary of the Good Friday Agreement next Easter has been touted. A senior diplomatic source said: “If you look at the calendar, you will come to the conclusion that next year might be an obvious reason to visit Europe, if things go well.”