Barcelona are looking to reinforce their formidable attack in the January transfer window, the Spanish and European champions' coach Luis Enrique said on Tuesday.

Barca have one of the most potent forward lines in world soccer in FIFA Ballon d'Or winner Lionel Messi, Neymar and Luis Suarez but lack a reliable replacement if any of the prolific South Americans are sidelined.

Academy graduates Munir el Haddadi and Sandro Ramirez are the only other recognised forwards in the squad but have failed to impress since their promotion from the B team.

"Right now our greatest need is to strengthen the attacking line but I would like bring in reinforcements across the board," Luis Enrique told a news conference previewing Wednesday's King's Cup last 16, second leg at city rivals Espanyol.

"Negotiations are tough in the winter market because nobody wants to let important players go," added the former Barca and Spain midfielder.

"We will try right up until the final day."

One option for Barca could be bringing back former Manchester City winger Denis Suarez.

A jewel in Celta Vigo's youth ranks, Suarez was chased by a number of top European clubs before he decided to join City in 2011 aged 17.

Opportunities for young players were slim and after a couple of seasons in which he made only a handful of first-team appearances he signed for Barca.

The 22-year-old performed well on loan at Sevilla in 2014-15 and has become an integral part of a Villarreal side who are riding high in fourth in La Liga.

Holders and record winners Barca take a 4-1 lead over Espanyol into Wednesday's Cup clash.

Recent meetings between the bitter local rivals have been brutal affairs and both Luis Enrique and Espanyol counterpart Constantin Galca have urged the players and fans to focus on playing football.

Barca's Uruguay forward Luis Suarez is banned for the game at Cornella-El Prat after he became involved in a fracas after the end of last week's first leg at the Nou Camp, during which Espanyol had two players sent off.

"Beyond the fact that we have an advantage, our goal remains to be superior to our opponent during the 90 minutes we are playing tomorrow," Luis Enrique said.

"We need to approach the match as if it was a single game (and not a two-legged tie). Playing Espanyol is always stimulating."

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