(Sharecast News) - Pottery outfit Portmeirion warned on full-year profits on Tuesday after some mixed trading in the first four months of the year, with good sales growth in its two largest markets being offset by a weaker than expected performance from its Korean operations.In the UK, sales were up 5%, while the US improved 8% yearn-year. Having had a very strong finish to 2018, Portmeirion anticipated slower demand in its export markets at the start of 2019, however actual export market sales, particularly for Korea, were even lower than the group had expected.Portmeirion said it was working with its Korean distributor on new product development during 2019, something it saw as "critical" to protect and grow the market for the long-term, but noted the development, by nature, would take time to bring to market and optimise for manufacturing efficiency."As a result, total group sales for the first four months of the year are down 10% against the comparative period last year," said Portmeirion"While the total effect on group sales is expected to be less than that for the full year, the board now expects profit before taxation for the full year will be significantly below market expectations."Finncap research director Peter Smedley said: "Despite investor weariness we predict that Portmeirion will bounce back. Investors will be reassured by the success of the business' diversification strategy in managing unexpected decline in 2016, as well as the continuation of their five-pronged growth strategy imperative."As of 0900 BST, Portmeirion shares had tumbled 25.51% to 905p.