Nov 16 (Reuters) - Illumina Inc (ILMN.O) on Tuesday defended the $8 billion purchase of Grail Inc (GRAL.O) as it gears up to battle formal objections raised by European antitrust regulators, which the company expects to be issued on Wednesday. The deal was finalised in August, and Illumina has said it would hold Grail, which makes a non-invasive, early detection biopsy test to screen for many kinds of cancers using DNA sequencing, as a separate company while waiting for approval from the EU. The European Commission last month had taken interim measures after Illumina closed the deal before its approval, including an order that Grail be kept separate. read more The bloc"s antitrust regulators will decide by Feb. 4 whether to clear it. The regulators have previously cautioned that the acquisition could curb innovation and competition.Menlo Park, California-based Grail has no presence in Europe and has no plans to enter the region for the foreseeable future, Illumina said on Tuesday in a briefing paper sent to all the national competition authorities in the European Economic Area. Any potential effects of the deal on competition in the region are therefore "remote and highly speculative," it said. Illumina announced the cash-and-stock deal for Grail last year, buying out investors including Amazon (AMZN.O) founder Jeff Bezos, to regain control of a company it spun out in 2016.