$Microsoft(MSFT.US)$ proposed $75 billion acquisition of $Activision Blizzard(ATVI.US)$ is likely to receive a close look from antitrust enforcers in the U.S. and abroad at a time when they have stepped up scrutiny of proposed mergers, especially in the tech sector.

The deal comes at a time of robust debate in Washington about whether the government should do more to restrain the nation's largest and most powerful tech companies. Despite Microsoft's size and role in the U.S. economy, as well as its history in the antitrust crosshairs in the 1990s, it has largely avoided the spotlight this time around. The Justice Department, the Federal Trade Commission and members of Congress have instead focused on alleged threats to competition presented by $Alphabet-A(GOOGL.US)$'s Google, $Amazon(AMZN.US)$, $Apple(AAPL.US)$ and $Meta Platforms(FB.US)$'s Facebook.

The Activision acquisition could give Microsoft a turn in the hot seat.

"Recent actions by the antitrust agencies in the U.S., but also recent, unprecedented aggressive actions abroad, including in EU and the U.K., probably suggest the agencies will take a close look at the transaction, " said former Justice Department antitrust chief Makan Delrahim.

Under the helm of Biden administration appointees, both the Justice Department and the FTC  have signaled their intent to scrutinize -- and potentially challenge -- a broader range of deals on the grounds that they threaten to reduce competition in the marketplace.

Hours after Microsoft announced its acquisition on Tuesday, the agencies said they would revisit government guidelines for reviewing proposed mergers. At a previously scheduled press conference, officials called for public input on ways they could strengthen the guidelines to combat unlawful mergers. The agencies said one area of focus was to better account for how deals in the digital marketplace affect competition.

Mr. Delrahim said Microsoft's and Activision's target 2023 closing date for the transaction appeared to be an acknowledgment that regulatory reviews may take a long time. One key question for antitrust enforcers, he said, is whether a combined Microsoft-Activision can better compete in videogames against foreign companies such as China's Tencent Holdings Ltd. and Japan's $Sony(SONY.US)$.

It isn't clear yet whether the Justice Department or the FTC will be the agency to review the transaction in the U.S. The two share antitrust enforcement authority and divvy up merger scrutiny.

Officials from both agencies declined to comment on the Microsoft deal.

The global videogame industry has been undergoing a wave of consolidation in recent years, and deal activity is off to a strong start this year. In addition to Microsoft's plans to buy Activision, last week $Take-Two Interactive Software(TTWO.US)$ said it reached an agreement to buy $Zynga(ZNGA.US)$ for $11 billion.

Microsoft was already on a game-studio buying spree. The company last year bought the owner of the popular Doom videogame franchise for $7.5 billion and before that it acquired several smaller ones. If it adds Activision to its portfolio, it will own a total of 30 game studios, up from 23 a year ago and up threefold since Satya Nadella became chief executive of Microsoft in 2014.

Microsoft gaming chief Phil Spencer said the company would still remain behind rivals Tencent and Sony Group in terms of revenue, adding that mobile phones are still the most predominant gaming device world-wide and "it's not a place where Microsoft has a unique capability."

The transaction, he said, would help Microsoft offset mobile platforms' control over videogame distribution. "We know we've got a long way to go to continue on our journey, which is really about reaching players," he said in an interview.

While Microsoft has a mobile version of its hit franchise Minecraft, the company doesn't otherwise have a big presence in mobile games, which last year generated more revenue than console and computer games combined.

Some consumer advocates raised immediate concerns about the deal.

"Once again, Microsoft, one of the biggest of the Big Tech companies, is shamelessly gobbling up a competitor to try to strengthen its market position," said Alex Harman of Public Citizen, a nonprofit consumer-advocacy group. "No way should the Federal Trade Commission and the U.S. Department of Justice permit this merger to proceed. If Microsoft wants to bet on the 'metaverse,' it should invest in new technology, not swallow up a competitor."

In Europe, the proposed merger is likely to face intense scrutiny. European Union competition regulators at the European Commission for several years have become increasingly wary of industry consolidation, particularly in acquisitions by tech giants. They are likely to look at Microsoft's post-merger total presence in the gaming business -- covering both gaming consoles and gaming software -- as well as the impact of synergies between Activision's games and Microsoft's Xbox.

Questions likely to arise include whether Microsoft's ownership of Activision Blizzard would create unfair competition against its main rivals in game hardware. The deal would allow Microsoft to offer more exclusive content on its Xbox consoles, potentially forcing consumers to choose them over Sony Group's PlayStation and Nintendo's Switch machines.

Some games from Activision's Call of Duty franchise, for example, have been on consoles from all three companies, and that might no longer be the case -- at least while consoles are still in vogue. The rise of cloud gaming, or the Netflix-like streaming of videogames, is expected to make consoles obsolete in the years to come, by providing access to games through more common devices such as smart TVs and mobile phones.