US Secretary of State Antony Blinken arrives in Kyiv after travelling overnight by train from Poland.

US Secretary of State Antony Blinken has arrived in Kyiv in a surprise diplomatic visit designed to underline the United States’s support for Ukraine as it battles to push back Russian troops who have opened a new front line in the northeastern Kharkiv region.

The trip is the first by a senior US official since Congress passed a long-delayed $61bn military aid package for the country last month, and amid concerns that the US government has been preoccupied with Israel’s war on Gaza.

Blinken, who arrived in Kyiv by train early on Tuesday morning, hoped to “send a strong signal of reassurance to the Ukrainians who are obviously in a very difficult moment”, said a US official who briefed reporters travelling with Blinken on condition of anonymity.

Blinken will meet Ukrainian President Volodymyr Zelenskyy and other senior Ukrainian officials “to discuss battlefield updates, the impact of new US security and economic assistance, long-term security and other commitments, and ongoing work to bolster Ukraine’s economic recovery,” the State Department said in a statement.

It is his fourth visit to Kyiv since Russia began its full-scale invasion in February 2022. He was last in the country in September last year.

Blinken’s arrival coincides with a renewed Russian push in the Kharkiv region and on the eastern front line as it seeks to take advantage of Ukraine’s weaknesses in munitions and manpower.

On Monday, US National Security Adviser Jake Sullivan said Washington was trying to accelerate “the tempo of the deliveries” of weapons to Ukraine and reverse the disadvantage that resulted from Congress sitting on the aid package for months.

“The delay put Ukraine in a hole and we’re trying to help them dig out of that hole as rapidly as possible,” Sullivan said, adding that a new package of weapons was going to be announced this week.

Artillery, air defence interceptors and long-range ballistic missiles have already been delivered, some of them to the front lines, said the US official travelling with Blinken.

Russia occupies about 18 percent of Ukraine.

It launched a new offensive in the Kharkiv region on Friday, forcing the evacuation of thousands of people.