The Trump administration has been increasingly critical of European nations, sparking concerns about America’s commitment to NATO and the continent.
Mr Trump has accused Sir Keir of doing “nothing” to end the conflict, and the two leaders are set to meet on Thursday for face-to-face talks.
The Telegraph reports that Sir Keir will use the trip to announce the date—most likely 2030—when the UK will spend 2.5% of its GDP on defence in an attempt to calm any tensions.
The Government has pledged to spend 2.5% but the path to this so far has been unclear.
Sir Keir is under growing pressure from UK political opponents to boost defence spending.
The US says European security is no longer its “primary focus” with Mr Trump calling on NATO members to spend 5%.
Alliance Secretary General Mark Rutte has suggested nations should be spending at least 3% of their national income.
The Telegraph reports the UK is drawing up a package of measures involving three different Government departments to support Ukraine, including the Ministry of Defence announcing new details of military aid and the Foreign Office unveiling a major set of sanctions.
Extra weapons are also under discussion but yet to be signed off, the newspaper reports.
Sir Keir says he is prepared to put British troops on the ground in Ukraine as peacekeepers to help enforce any peace deal made to end the bloody conflict.
British troops deployed to Romania told the Daily Express earlier this week that they are prepared and willing to go to Ukraine if required.
