PARIS The first launch of Europe's new Ariane 6 rocket has slipped into 2024 after an incomplete recent ground test, the head of the European Space Agency suggested in remarks to Reuters.

ESA and manufacturer ArianeGroup, owned by Airbus and Safran, have been carrying out ground tests at the Kourou spaceport in French Guiana and in Germany for the new launcher, which is needed to fill a gap in space access after the retirement of Ariane 5 and recent failure of the smaller Vega C launcher.

Part of the last test run on July 18 - a short hot firing of the Vulcain 2.1 engine - was not completed and has been postponed to Aug. 29, ESA said last week in an invitation to a Sept 4 media briefing. Ninety percent of July's objectives were met and further tests are scheduled for September, it added.

"After this series of tests we plan to consolidate a launch date for Ariane 6," ESA Director General Josef Aschbacher told Reuters.

Asked whether it was fair to assume that plans for a test launch before the end of the year were now out of reach, Aschbacher told Reuters, "This is fair to say, yes".

In June, Airbus Chief Executive Guillaume Faury told the Paris Air Forum that first test launch of the new heavy Ariane 6 launcher was scheduled for the end of the year, but that this would depend on the progress of ground tests during the summer.

Aschbacher was speaking during an interview in which he urged European politicians to ignore pressure to weaken climate targets, saying record heat waves and fires visible from space provided "really alarming" evidence of global warming.

(Reporting by Tim Hepher. Editing by Gerry Doyle)