The next version of the Firefox Web browser (Firefox 1.5) will ship later this summer.

In this release, developers are building new features, including an automatic update service.

Chris Hofmann, lead engineer at The Mozilla Foundation said: "There really hasn't been any official date" for a release, Hofmann said. "We haven't ever published a date." Instead, the target time frame for a new release has always been mid- to late summer, he said.

Although the next release of the Firefox 1.0 browser has generally been referred to until now as Version 1.1, that nomenclature is now being changed to Version 1.5. The reason, Hofmann said, is that it will be easier for developers to test interim versions of the software using a wider gap in the version numbers.

So far, developers are making good progress in adding features to the upcoming version of Firefox, including development features that can be used to encourage additional Web applications for the browser, Hofmann said.

First and second alpha releases of the application were released last month, and a beta version is expected soon. But no specific date has been offered for when the beta will be available.

Earlier this week, The Mozilla Foundation announced that international versions of Firefox and the Thunderbird email client would be delayed so that several recent security fixes could be included. The delay arose from a number of software glitches that were introduced in last week's release of English-language versions of Firefox and Thunderbird.

The open-source browser was released in November for free download and has grown as a popular alternative to Microsoft's Internet Explorer browser.

By April, Firefox had been downloaded 50 million times.