The Foreign Office says the trip is being put off because a NATO foreign ministers meeting is being rescheduled.
The NATO meeting had been scheduled for April 5-6, but last week officials said it would be rescheduled so US Secretary of State Rex Tillerson can attend. The alliance says the meeting will now take place tomorrow.
Tillerson had said he would skip the semiannual meeting of the military alliance and would instead travel to a Group of 7 meeting in Italy and then to Russia.