British government officials will meet with representatives of American technology companies this week to demand that they do more to help in the fight against terrorism and online hate speech, the latest move in a widening global push against encryption technology that blocks access to the private messages of criminal and innocent users alike.

The meeting, set for Thursday, comes after Amber Rudd, Britain’s home secretary, said that the country’s intelligence agencies should have access to encrypted messages sent through WhatsApp, an instant-messaging service owned by Facebook. Her remarks are in response to the terrorist attack on Wednesday in London, when Khalid Masood, a 52-year-old Briton, drove a car into pedestrians, killing three of them, and then fatally stabbed a police officer.

The Islamic State claimed responsibility for the attack, but its precise connection to Mr. Masood is not clear.

The London police said on Monday that they were focusing on Mr. Masood’s communications and repeated a plea to anyone who knew him to come forward with tips.

