BlackRock's assets under management hit a record high for the third straight quarter as a U.S. stock market rally boosted inflows, while the world's largest asset manager continued a push to expand its footprint in private markets.

Stocks at record levels and robust bond markets should set up BlackRock to report a record amount of assets under management when it discloses its quarterly earnings on Friday, even as Wall Street analysts say profits will slip from a year ago and fees will remain under pressure.

Assets under management at BlackRock have topped $11trn, the US investment giant confirmed on Friday, a fresh high.