Antony Blinken arrived in the Ukrainian capital by overnight train from Poland and is due to meet President Volodymyr Zelensky on Wednesday, his fourth visit to Kyiv since Russia invaded in February 2022. Blinken is also set to meet his Ukrainian counterpart Dmytro Kuleba and deliver a speech focused on "the future of Ukraine" to civil society groups, a senior US official said on the train. The idea is to highlight "Ukraine's successes" following a speech Blinken gave in Helsinki in June 2023, in which he stressed Russia's "strategic failure", said the official, who asked not to be named. Among the issues under discussion will be a bilateral defence agreement that the US hopes to conclude before a NATO summit in Washington in July. "The negotiations are in the final stages. We are very close," the official said. The visit is intended to "send a strong signal of reassurance to the Ukrainians who are clearly in a very difficult moment, both because of the intensified fighting in the east, but also because the Russians are now escalating their cross-border attacks on Kharkiv," the official said. Russia on Friday launched a surprise offensive near Ukraine's second city of Kharkiv in the northeast, claiming five villages in the Kharkiv region and one in Donetsk. "It's clear that they (the Russians) are throwing everything they have at the east, and the extension of the fighting to Kharkiv is part of this strategy of throwing everything they have at the Ukrainians," the US official said. "But we are confident that the Ukrainians will continue to make progress in pushing back the Russians as the assistance from the United States and other allies and partners continues to flow," the official added. Blinken's surprise visit comes just weeks after the US Congress approved a $61 billion military aid package for Ukraine, following months of deadlock. The US has since sent nearly $1.4 billion worth of military assistance to Ukraine, mostly air defence systems and artillery ammunition, some of which is already at the front, the official said. Blinken will notably "detail how our assistance is going to be calibrated to strengthen their defences and allow them to seize the initiative" on the battlefield, he added. Read Also: Kyiv pede rapidez aos EUA na entrega de armas para defender Kharkiv (Portuguese version)