Economist Paul Krugman thinks that if Japan's sales tax reaches 10%, it could mean a disastrous return to deflation.

In an interview published this week in Shukan Gendai, a weekly Japanese magazine, Mr. Krugman, a Princeton University economist and New York Times columnist, weighed in on Prime Minister Shinzo Abe's economic policy as Mr. Abe's administration closes in on the two-year mark in December.

Saying that Mr. Abe has listened to the wrong people, Mr. Krugman argued that Japan's economic recovery has been thrown into doubt by the April increase in the national sales tax to 8% from 5%, according to the Japanese-language article. The magazine didn't make his comments available in English.

Mr. Abe is weighing whether to go ahead with plans for a further increase to 10% in October 2015. Mr. Krugman, a Nobel laureate in economics, said the prime minister should go in the opposite direction and cut the rate back to 5%, then work to raise inflation expectations.

This will come as no surprise to longtime readers of Mr. Krugman's views on Japanese economic policy. Back in 1998 he argued, "Unless one can make a convincing case that structural reform or fiscal expansion will provide the necessary demand, the only way to expand the economy is to reduce the real interest rate; and the only way to do that is to create expectations of inflation."