ABU DHABI (Reuters) - Opec is concerned about crude oil prices that have lost more than a quarter of their value since June, but is not panicking, the United Arab Emirates energy minister said on Tuesday.

Brent crude fell towards US$84 a barrel on Tuesday, after top oil exporter Saudi Arabia cut prices to the United States.

The cut had hammered oil prices on Monday as it underscores Saudi efforts to fight for market share in the world's largest oil consumer while raising prices to Asia and Europe.

The absence of signs that the Organization of the Petroleum Exporting Countries (Opec) could curb output also continued to weigh on sentiment as abundant supplies of high-quality oil such as US shale have overwhelmed demand in many markets, filling stocks worldwide.

"Yes we are concerned but we are not panicking," Mr Suhail bin Mohammed al-Mazroui told Reuters when asked if he was worried about the recent decline in global oil prices.

He declined to say if Opec would cut output when it meets on Nov 27 in Vienna. The gathering is shaping up to be one of Opec's most important in years.

"As I said before let's wait, we are having a meeting at the end of the month," the minister said on the sidelines of an industry event in Abu Dhabi. "We as a group of producers are not the only ones producing, there are others. Our role is to balance the market with supply, this is what we will always do."

While some Opec members have voiced concern over the drop in prices, indications are that OPEC is unlikely to cut its output target.

Opec's secretary-general said last week that Opec's oil production is unlikely to change much in 2015.

Opec members Iran and Kuwait have said a cut in output at the next meeting was unlikely. Saudi Arabia has yet to comment publicly.