Oil prices have fallen following the closing of nuclear negotiations between Iran and six world powers that would end sanctions against the country.

Brent crude for August slipped $1.89 to a low of $56.84 a barrel, while the US light crude, also known as West Texas Intermediate (WTI), declined $1.15 at $51.59 a barrel, Reuters reported.

Negotiations have reached the make-or-break point and there are other final issues that need to be sorted out.

Disagreements regarding the accurate timing and sequencing of sanctions relief for Iran in addition to the continuation of an arms and ballistic-missile ban are the final issues that are yet to be resolved.

"Implementation risks remain, and a possible nuclear deal with Iran should limit the upside."

The nuclear deal is expected to release Iranian oil into oversupplied markets, which held down prices.

Some analysts forecast a decline in oil price due to the probability of addition oil barrels already oversupplied oil market, especially when there is a weak demand.

Bank of America’s Merrill Lynch said in the third quarter of 2015, crude prices in the US could decline well below its target of $50 per barrel.

Elsewhere, Greece Prime Minister Alexis Tsipras confirmed that an agreement with its creditors secured the country debt restructuring and medium-term financing in a growth package which is worth €35bn ($38.7bn).

Commerzbank Frankfurt senior oil and commodities analyst Carsten Fritsch told the news agency: "Implementation risks remain, and a possible nuclear deal with Iran should limit the upside."

Analysts believe that Iran would be able to return to full-scale exports by 2016.

In the short-term an increase of around 200,000 barrels a day in exports is expected to add to an existing surplus of about 2.6 million barrels a day.