"I have authorised the deployment of additional military personnel to support the diplomatic presence in Kabul, assist British nationals to leave the country and support the relocation of former Afghan staff who risked their lives serving alongside us," Defence Secretary Ben Wallace said.
The government last month eased the rules to allow people from amber countries fully jabbed with a vaccine approved by regulators in the United States and European Union to enter without having to self-isolate.
Expectations that Britain's economy will reopen quickly after its rapid vaccine rollout lifted sterling to $1.42 in February, at the time making it the best performing G10 currency.
The ministry also noted ongoing naval operations with NATO allies in the Baltic, and the deployment to Asia later this year of a carrier strike group led by the country's new aircraft carrier.