The Russian, who served a 15-month doping suspension after failing a test for meldonium last year, was playing in her first match at a major since returning to competition in April.

It proved a thrilling dual between two players more suited to meeting in the final stages of a Grand Slam rather than in the first round.

Sharapova, the 2006 US Open winner ranked 146th in the world, took the first set 6-4 as her pace proved too much for Halep's impressive speed around the court.

The Romanian hit back to win the second set 6-4.

But it was Sharapova who won the deciding set 6-3 in front of almost 24,000 people at Flushing Meadows.

"You never know what you're going to feel until you win that match point, but everything you go through is worth it for this moment," she said afterwards.

"You sometimes wonder why you put in all the work, and this is exactly why."

Sharapova, who now boasts a 7-0 record against Halep, will next face world number 58 Timea Babos of Hungary.

A second shock result in the women's singles draw today saw Britain's seventh seed Johanna Konta defeated in three sets by Serbian Aleksandra Krunic.

The world number 78 fought back from a set down to seal a 4-6, 6-3, 6-4 victory.

Wimbledon champion Garbine Muguruza avoided any surprise.

The Spanish third seed beat Uzbek-born naturalized American Varvara Lepchenko 6-0, 6-3 to reach the second round.

Two-time champion Venus Williams also progressed after beating Slovakian teenager Viktoria Kuzmova 6-3, 3-6, 6-2.

Men's singles favourites Roger Federer and Rafael Nadal will each begin their respective campaigns tomorrow.