Prices began dropping early on euro zone worries triggered by Spain’s debt problems and weekend talks between Iran and six world powers about its disputed nuclear program.

Negotiators from Iran and the six nations that met in Istanbul agreed to reconvene on May 23 in Baghdad and Iran’s foreign minister said his country was ready to resolve all nuclear issues in the next round of talks if sanctions against Tehran were lifted.

The owners of the Seaway crude oil pipeline plan to begin reversing its flow by May 17, earlier than previously expected, if they get regulatory approval from the Federal Energy Regulatory Commission (FERC). The pipeline will initially carry about 150,000 barrels per day from the Midwest to the Gulf Coast, helping ease the glut of oil in the region.

“The earlier-than-expected reversal of the Seaway pipeline has triggered selling of the WTI-Brent spread,” said Gene McGillian, analyst at Tradition Energy in Stamford, Connecticut.

In London, Brent crude for June delivery was down $2.45 at $118.76 barrel, by 1:55 p.m. EDT (1755 GMT), after dropping to a session low of $118.20, the lowest for front-month Brent since Feb. 15.

US crude for May delivery which expires on Friday, shifted higher and was up 22 cents at $103.05 and the June contract rose 12 cents to $103.44.

June Brent’s premium against its counterpart US contract stood at $15.32, after dropping to $15.14 earlier, the narrowest since Feb. 29. On Friday, the spread closed at $19.

In recent months, higher production in the Midwest had created an oversupply, depressing US benchmark crude futures, also known as West Texas Intermediate (WTI), relative to global benchmark Brent crude.

Spain’s 10-year government bond yields topped 6 percent for the first time this year as investors worried about the country’s ability to contain its budget deficit, putting the eurozone’s debt troubles once again in the spotlight.

“The overall mood is one of risk aversion after the news from Spain,” said Eugen Weinberg, an energy analyst at Commerzbank in Frankfurt.

The euro retreated broadly on concerns about Spain’s economy, falling to a two-month low against the US dollar.

The drop in oil prices followed losses on Friday spawned by lower-than-expected first quarter economic growth in China, the world’s largest energy consumer.

US heating oil futures slid more than 6 cents, or nearly 2 percent in early trading, helping pull down US crude futures.

Heating oil tumbled as demand for heating oil was forecast to average 55 percent below normal this week, with warm springtime temperatures forecast in the US Northeast, the biggest market for heating oil.

Market focus remained on Iran as traders awaited a breakthrough in the talks. Iran’s tensions with the West over its nuclear program was a major reason crude futures have risen to this year’s high of more than $128 for Brent and $110 for US crude, both on March 1.

A European Union import ban on Iranian oil is set to start July 1.

“Iran is back at the negotiating table, which has reduced the possibility of immediate attacks on Iranian installations or a blockade of the Straights of Hormuz, so the geopolitical premium in Brent is waning,” said Commerzbank’s Weinberg.

The US remained on guard and President Barack Obama said more sanctions would be imposed against the Islamic Republic if there was no breakthrough in nuclear talks with global powers in the coming months.