Kyiv. British Prime Minister Keir Starmer arrived in Kyiv on Thursday, pledging to help guarantee Ukraine's security for the next century, just days before Donald Trump is sworn in as U.S. president.

The British government announced that Starmer and Ukrainian President Volodymyr Zelenskyy will sign a "100-Year Partnership" treaty in the Ukrainian capital. The agreement will cover key areas such as defense, science, energy, and trade.

This unannounced visit marks Starmer's first trip to Ukraine since becoming prime minister in July. He previously visited Ukraine in 2023 as opposition leader and has twice met with Zelenskyy in London since taking office.

On a cold and gray morning, Starmer was greeted at Kyiv's railway station by the UK ambassador to Ukraine, Martin Harris, and Ukraine's envoy to London, Valerii Zaluzhnyi.

The United Kingdom, one of Ukraine's largest military backers, has provided £12.8 billion ($16 billion) in military and civilian aid since Russia launched its full-scale invasion three years ago. More than 50,000 Ukrainian troops have been trained on British soil. During his visit, Starmer is expected to announce an additional £40 million ($49 million) to support Ukraine's postwar economic recovery.

Despite the UK's significant contributions, its role is overshadowed by that of the United States. Uncertainty looms over the future of US aid to Ukraine after Trump takes office on Jan. 20. The president-elect has questioned the costs of U.S. support for Kyiv, expressed a desire to end the war swiftly, and plans to meet Russian President Vladimir Putin, for whom he has shown admiration.

Ukraine's allies have rushed to bolster support ahead of Trump's inauguration, aiming to place Kyiv in a stronger position for any potential peace negotiations. Zelenskyy has emphasized the need for assurances about Ukraine's future security in any peace deal with Russia, a much larger neighbor that annexed Crimea in 2014 and launched a full-scale invasion in February 2022.

The proposed 100-year partnership treaty is part of the UK's effort to provide such assurances. The deal will focus on defense cooperation, including maritime security in the Baltic, Black, and Azov Seas, and joint technology projects like drone development—essential tools in the ongoing conflict. It also includes a system to track Ukrainian grain stolen by Russia and exported from occupied territories.

“Putin's ambition to wrench Ukraine away from its closest partners has been a monumental strategic failure. Instead, we are closer than ever, and this partnership will take that friendship to the next level,” Starmer said before the visit.

“This is not just about the here and now—it is an investment in our two countries for the next century, advancing technology, scientific research, and cultural exchanges while harnessing Ukraine’s remarkable innovation for generations to come,” he added.

Starmer and Zelenskyy are also expected to discuss a proposal by French President Emmanuel Macron to deploy Western troops in Ukraine to oversee a ceasefire agreement. Zelenskyy has insisted that any such plan must include a timeline for Ukraine's NATO membership. Although NATO's 32 member states have agreed that Ukraine will eventually join the alliance, this is unlikely to happen until after the war ends.

Trump has expressed sympathy for Putin's opposition to Ukraine joining NATO, further complicating the dynamics of the conflict.

As the war approaches its three-year mark, both Russia and Ukraine are striving for battlefield gains to strengthen their positions in potential peace talks. Ukraine has launched a second offensive in Russia’s Kursk region, aiming to hold onto territory captured last year, and has intensified drone and missile attacks on Russian military targets.

Meanwhile, Russia continues its slow advance on the 600-mile (1,000-kilometer) front line in eastern Ukraine, incurring high casualties. Moscow has also escalated attacks on Ukraine's energy infrastructure, aiming to deprive civilians of heat and light during the harsh winter. On Wednesday, a major Russian missile barrage forced authorities to shut down power grids in several regions.