Manchester United's Ander Herrera says "favourites" Manchester City face intense pressure to win the Premier League after their summer spending spree and trophyless campaign last season.

The Manchester clubs are joint top of the table with exactly the same record -- 13 points from five games and a plus-14 goal difference.

United won the Europa League, League Cup and Community Shield in Jose Mourinho's first campaign at the helm but finished a disappointing sixth in the league.

City ended third in the Premier League after a fine start under Pep Guardiola petered out in an ultimately trophyless campaign.

Abu Dhabi-owned Manchester City spent the most of any Premier League club during the summer transfer window -- £215 million ($290 million, 242 million euros) while United splashed out more than £140 million.

"Man City have spent the biggest amount in the Premier League so they are the principle contenders for the title," said Herrera.

"We will try to be there as well. We have quality as well and we will fight for every title. But I think because of the money they have spent they are the favourites."

The United midfielder, who has struggled for time on the pitch this season, added: "We won three titles last season and City didn't win anything. They are under pressure.

"They are obligated to win titles. We won three last season so they have more obligation than us. But you know when you play for Man United, winning is an expectation and an obligation but I like that obligation to be honest."

United kick off their defence of the League Cup against Burton Albion on Wednesday and Sergio Romero may get his first run out of the season in place of the ever-impressive David De Gea.

Herrera believes De Gea is the best goalkeeper in the world but says United need to win trophies in order to ensure they keep the player, who has frequently been linked with a move to Real Madrid.

"Of course I can see him staying here for more years. How good is David now? We need to win titles to keep him with us. That is what we did last season," he said.

"Real Madrid are going to talk about it every summer because he is the best 'keeper in the world. But we don't think we are far from Real Madrid. We won three titles last season, the only English team to do it," he added.