The retailer, which includes supermarket Waitrose released positive Christmas figures on 12 January.
Chairman Sir Charlie Mayfield said: "Although we expect to report profits up on last year, trading profit is under pressure. This reflects the greater changes taking place across the retail sector. We expect those to quicken, especially in the next 12 months as the effects of weaker Sterling feed through. We will now accelerate aspects of our strategy. This will involve a period of significant change, investment and innovation to ensure the Partnership's success."
JLP said: "The most obvious of these changes is the channel shift from shops to online. The other major influence is pricing, where deflation continues in food and non-food, despite rising input costs as a result of weakness in the Sterling exchange rate.
"These factors are significant for the outlook where we expect both inflationary cost pressures and competition to intensify in the market as a whole. The rate of retail market sales growth may slow and the rate of profit growth that is achievable will be affected by margin pressure.
"We have decided to comment on Bonus implications at this stage because the Partnership's strong Christmas trading, and the likelihood of higher reported profits, risk overshadowing the importance the Board is placing on the challenging market outlook, our determination to maintain a strong balance sheet and our commitment to accelerating our strategy. The precise level of the Bonus will be decided as usual in March, but, in view of these factors, it is likely to be significantly lower than last year."
John Lewis Partnership plc will report its full year results ended 28 January 2017 on 9 March 2017.
John Lewis saw online sales up 11.8 per cent, representing 40.0 per cent of sales, with shop sales up 0.8 per cent in the six weeks to 31 January.
Waitrose saw gross sales (excluding fuel) up 4.8 per cent to £914.9m, with like-for-like sales up 2.8 per cent. Best in class and hospitality sales did best. The company predicts "the outdoors will come indoors" this spring.