A formal invitation for a state visit, issued by the monarch on the advice of the government, is among the heaviest tools in Britain’s diplomatic arsenal. Delegations are invited to stay for several days, and the visits often include meetings with the government and other public engagements. Before Mr. Trump, Barack Obama and George W. Bush were the only two American presidents who had been invited to Britain for a full state visit.

The date of the visit will coincide with events for the 75th anniversary of the D-Day landings in Normandy in 1944.

Mr. Trump mostly avoided London on his last visit, when protesters made it clear that he would not be welcome in the capital.