However, he has also warned of impending job losses in a message to staff confirming the bakery chain's intention to have returned to full service by next month.
In the message, Whiteside said that Greggs' manufacturing capabilities were returning to normal.
He also announced that Greggs would be featured in the Just Eat ad campaign at the end of this week, with coverage increasing throughout September as the business moves to expand its click and collect and delivery programme nationally.
It was first reported back in January that Greggs had exclusively partnered with Just Eat as part of a plan to roll out delivery nationwide.
With regards to the issue of job security, Whiteside warned of potential job losses once the furlough scheme comes to an end in October.
“As I have said previously, we cannot expect to trade normally under social distancing constraints, and we will make full use of the government furlough scheme to give us time to establish how close to normal trading we can achieve, and therefore hopefully minimise any impact there may be on employment prospects for colleagues,” he said.
“As the furlough scheme tapers down, we are now contributing to colleague pay at an increasing level each month, and we will continue to do so until the scheme ends in October.
“However, we will not be in a position to continue funding furlough pay once the scheme ends and, on this basis, we must accept that it is highly probable that we will need to propose job losses.
“We are working behind the scenes to review current staffing levels in every part of our business – Retail, Supply and Greggs House, and to understand what the future need may be in light of the changes in trading conditions we have seen and what we anticipate is to come.
“I hope that this work will be completed in the next three weeks and I will update you again on September 15. I understand that this is an uncertain time for all our colleagues and I am sorry that I am not in a position to provide you with any more information at the moment.
“I hope that you understand it would be premature of me to speculate about what the outcome of the review may be, whilst it is ongoing. We also hope that in the coming weeks our trading performance will continue to improve, which could positively impact on our next steps.
"Let me reassure you that our aim is to protect as many jobs as we can.”