Manchester United have signed Brazil left-back Alex Telles on a four-year deal from Porto, with the option of a further year.

The 27-year-old, who has one cap for his country, moves to Old Trafford for a fee of 15m euros (£13.6m) plus 2m euros (£1.8m) in add-ons.

Telles scored 26 goals and made more than 50 assists for Porto after joining them from Galatasaray in 2016.

He said joining United, a club with "prestige", was a "huge honour".

"You have to work hard to get to this moment in your career and now I am coming to this club, I can promise that I will give everything in my heart to be a success here," he added.

"I won many trophies at FC Porto and I want to continue that at United. The manager has a clear plan and direction for this team and I can't wait to pull on the famous shirt."

United manager Ole Gunnar Solskjaer said: "First and foremost I welcome Alex to United. He is a player we have been tracking for some time and his performances over the past few years are exactly what we are looking for.

"He is a fighter and a winner and will add real determination and competition to the squad. Alex has the qualities, both as a player and as a person, that we want here at Manchester United."

Telles is United's second signing of the summer transfer window after the arrival of Netherlands midfielder Donny van de Beek from Ajax in September.

United are closing in on a deal to sign Uruguay striker Edinson Cavani, who is a free agent after leaving Paris St-Germain, while they are also in talks to sign Atalanta winger Amad Traore.

In addition, Chris Smalling's on-off permanent move to Roma is back on after the 30-year-old defender spent last season on loan at the Serie A side.

After a day of waiting for developments, an agreement over a fee appears to have been reached which would allow the deal to go through.

However, with the Italian transfer window closing at 19:00 BST, there is now a race against time to get all the paperwork done.