The Organisation of the Petroleum Exporting Countries (OPEC) met in Vienna to decide its production policy in coordination with non-OPEC producers including Russia, Oman and Kazakhstan.
An OPEC delegate said the organisation had agreed a tentative deal to cut oil output but had not yet come up with a final figure.
Saudi Energy Minister Khalid al-Falih said earlier that OPEC needed Russia to come on board with any cuts. He said a final decision by OPEC and its allies was likely by Friday evening.
Expectations had been for a joint cut of between 1 and 1.4 million barrels per day (bpd). Falih said before the meeting that the "OPEC+" group would be happy with a cut of just 1 million bpd.
Brent crude futures were down $2.07 on the day to $59.49 a barrel by 1532 GMT, having hit a session low of $58.36, while US futures fell $1.38 to $51.51 a barrel.
The two have lost 30 percent in value this quarter alone.
"The real impact of the meeting will be evident tomorrow following the release of the OPEC+ joint declaration," said Abhishek Kumar, Senior Energy Analyst at Interfax Energy
"Countries participating in the agreement will have to cut their combined output by at least 1 million bpd from the October 2018 level in order to have a meaningful bullish effect on oil prices."
Led by Saudi Arabia, OPEC's crude oil production has risen by 4.1 percent since mid-2018, to 33.31 million bpd.
"(OPEC) know how to handle markets. They might be talking it down and then delivering a sucker-punch a bit later, that could also be the outcome," Saxo Bank senior manager Ole Hansen said.
European equities hit their lowest in two years and commodity-sensitive currencies such as the Russian rouble fell sharply, in part because of the slide in the oil price, but also with the arrest of a top executive of Chinese tech giant Huawei in Canada for extradition to the United States
The arrest of Huawei's chief financial officer Meng Wanzhouof, who is also the daughter of the firm's founder, triggered renewed fireworks just as Washington and Beijing prepare for crucial trade negotiations.
Barclays said in its Global Outlook published on Thursday that "investors need to lower their expectations" and that "2019 should be a period of lower returns and higher volatility".
Barclays said it expected "the global economy to slow over the next several quarters" although it added that "not one major economy is near recession."