Former British Prime Minister Boris Johnson will meet with Republican lawmakers this week as he presses the United States to sustain aid to Ukraine as it fights off Russia's assault.

Johnson is scheduled to speak at a private Republican club in Washington on Tuesday evening, said Representative Joe Wilson, a member of the House of Representatives Foreign Affairs Committee. He is also scheduled to meet with a group of Republican senators, said U.S. Senator Todd Young on Monday, though he said he was unaware of the exact timing of the talks.

On Wednesday, Johnson will discuss the need for "Western unity and support for Ukraine and what more can be done against the threat Russia poses" at the Atlantic Council think tank.

The Republicans took over the House from the Democrats at the start of this year and some hardline members of the Republican conference have called for an end to U.S. military and other assistance to Ukraine, which amounts to tens of billions of dollars.

Johnson, who left office in September following a series of scandals, was prime minister when Russia invaded Ukraine in February last year. He sought to position the UK as Ukraine's top ally in the West and has continued to do so.

During a trip to Ukraine this month, Johnson visited Borodyanka and Bucha, suburbs of the capital Kyiv that became a byword in the West for Russian atrocities. Moscow denies allegations by Ukraine and its Western allies that it has committed war crimes.

In a Washington Post opinion piece published on Monday, Johnson argued for the admission of Ukraine to the NATO security alliance.

"Ukrainians should be given everything they need to finish this war, as quickly as possible, and we should begin the process of admitting Ukraine to NATO, and begin it now," he wrote.

Wilson, who will be among the lawmakers meeting Johnson, is a staunch Ukraine supporter, having even suggested the placement of a bust of Ukrainian President Volodymyr Zelenskiy in the U.S. Capitol.

Johnson's office did not respond to a request for comment, nor did the office of House Speaker Kevin McCarthy, the top Republican lawmaker.