Amazon unveiled the new tablets last month, but the devices had not secured FCC clearance. The company had to put disclaimers on Web pages and emails promoting the products.

FCC approval is required for wireless communications devices to assure that they operate safely and do not improperly interfere with other signals.

The new gadgets are important for Amazon as the world's largest retailer tries to compete with Apple Inc for a slice of the booming tablet market.

Amazon brought out a cheap 7 inch Kindle Fire last year, but the new versions come in larger sizes and the most expensive models sport 4G LTE wireless connectivity.

Last month, attorneys and analysts familiar with FCC compliance procedures said the FCC was unlikely to reject the Amazon devices out of hand, or prolong the approval process past its shipping date.

But they said it was unusual for a company to announce major new products without first getting the sign-off from the agency.

Amazon is accepting pre-orders now and plans to ship the 4G devices on November 20. A company spokeswoman said last month that Amazon expected to receive FCC approval before November 20.

(Reporting by Alistair Barr; Editing by Gary Hill and Andre Grenon)

• A Permanent Economic Emergency