Defending champion Daniil Medvedev made a winning start on his US Open return as he recorded a straight-set victory over American Stefan Kozlov.

He claimed his first Grand Slam title in New York last year by beating Novak Djokovic, who is not allowed to play.

He will play Frenchman Arthur Rinderknech in the second round in New York.

Elsewhere in the men's draw, Britain's 2012 winner Andy Murray beat Argentine 24th seed Francisco Cerundolo 7-5 6-3 6-3.

Spanish 16th seed Roberto Bautista Agut suffered a shock first-round exit against American JJ Wolf, losing 6-4 6-4 6-4.

There are four men's players who could replace Medvedev as world number one following the US Open, including Spaniard Rafael Nadal, who is seeking a 23rd major title.

Medvedev was banned from competing at Wimbledon this summer because of Russia's invasion of Ukraine, though he remained the top-ranked men's player after the grass-court Grand Slam was stripped of its ranking points because of that decision.

Returning to action at a major - though not permitted to compete under the Russian flag - Medvedev secured victory in emphatic fashion as he closed out the match by winning eight successive games.

Kozlov, ranked 111st, responded immediately to having his serve broken in the first two sets but Medvedev pulled clear on both occasions before his opponent fell away in the third.