Feb 8 (Reuters) - Illumina on Thursday forecast its annual core business revenue to be nearly flat compared to fiscal year 2023 as subdued demand for its genetic testing tools and diagnostics products extends into this year.

The gene sequencing machine maker has witnessed a year of sluggish demand for its tools and services due to cautious customer spending and a protracted recovery in its key market, China.

The company's fourth-quarter revenue was $1.12 billion, compared with an estimate of $1.09 billion, helped by strong demand for its consumables and DNA sequencing instruments, NovaSeq X.

It shipped 79 units of the instrument during the quarter and 352 for the full year 2023.

The gene sequencing company said it is focusing its financial outlook on core Illumina, as the specific timing and impact of its Grail divestment remains uncertain.

The U.S. life sciences company's core segment, which excludes Grail, advances sequencing instruments, consumables and services for genetic analysis to hospitals, biotech and pharmaceutical companies for disease research and drug development process.

Shares of the San Diego, California-based Illumina fell 2.7% to $139.5 in extended trading. The stock lost more than 30% of its value in 2023.

On an adjusted basis, it earned per share profit of 14 cents during the quarter ended Dec.31, versus analysts' average estimate of 2 cents.

Illumina said in December that it will divest cancer diagnostic test maker Grail after the companies ran afoul of U.S. and European antitrust enforcers for more than two years and faced fierce opposition from activist investor Carl Icahn.

Terms of the divestiture are expected to be finalized by the second quarter of 2024.

(Reporting by Pratik Jain in Bengaluru; Editing by Tasim Zahid)