SAN FRANCISCO (Dow Jones)-Amazon.com Inc. (AMZN) Chief Executive Jeff Bezos said Thursday that he sees a lot of opportunity to eliminate waste and improve productivity at the Internet retail giant.

"Everywhere we look, and every team here looks, when we look we find that we are doing every operation that we do in suboptimal ways. We can get variable and fixed productivity for a long time to come," said Bezos.

Bezos made his comments during a conference call with analysts after the company reported strong first quarter results but provided slightly disappointing second-quarter guidance.

Citi analyst Mark Mahaney said Amazon's results were "truly impressive" given the economic environment. He noted that the pro forma operating margin was up 40 bps year-over-year at 6.6%, sharply higher than Wall Street analysts' expectations of 5.6%.

But he noted that Amazon's guidance implied the company would report $4.53 billion in revenue, below analysts' consensus, and its margin would drop to about 5.3% in the second quarter.

Chief Financial Officer Tom Szkutak told analysts that the impact of Easter falling in the second quarter, as well as foreign exchange trends would translate into lower operating income.

"Seasonally Q2 is our lowest quarter from a revenue perspective, which means with that top line, you get a little bit less leverage, in particular the fixed operating costs," he said.

-By Scott Morrison; Dow Jones Newswires; 415-765-6118; scott.morrison@dowjones.com