Oil futures rose on Friday on course for a fourth weekly gain boosted by supply constraints and a weaker dollar and despite sources saying China is set to release crude reserves around the Lunar New Year.

Brent crude futures rose 71 cents, or 0.8%, to near a two-and-a-half month high of $85.18 a barrel at 1430 GMT. U.S. West Texas Intermediate crude gained 57 cents, or 0.7%, to $82.69.

Crude prices turned positive as the dollar headed towards what could be its largest weekly fall in more than a year. A weaker dollar makes commodities more affordable for holders of other currencies.

Several banks have forecast oil prices of $100 a barrel this year, with demand expected to outstrip supply, not least as capacity constraints among OPEC+ countries come into focus. “When you consider that OPEC+ is still nowhere near pumping to its overall quota, this narrowing cushion could turn out to be the most bullish factor for oil prices over the coming months,” said PVM analyst Stephen Brennock.

However, sources told Reuters that China plans to release oil reserves around the Lunar New Year holidays between Jan. 31 and Feb. 6 as part of a plan coordinated by the United States with other major consumers to reduce global prices.

The US Energy Department on Thursday said it had sold 18 million barrels of strategic crude oil.

China has also posted its first annual decline in crude oil imports in two decades, though traders expect imports to recover this year.

There were also concerns about fuel demand in the world’s second-biggest oil consumer as the Omicron coronavirus variant spread to the cities of Dalian and Tianjin.

Many cities, including Beijing, have urged people not to travel during the Lunar New Year holiday, which could cool demand.

Meanwhile, China’s politically volatile global trade surplus surged to $676.4 billion in 2021, likely the highest ever for any country, as exports jumped 29.9% over a year earlier despite semiconductor shortages that disrupted manufacturing.

The country’s monthly trade surplus in December swelled 20.8% over a year earlier to a record $94.4 billion, customs data showed Friday.

China piled up a series of monthly export surpluses in 2021 but they prompted less criticism from the United States and other trading partners than in earlier years while their governments focused on containing coronavirus infections.

Exports rose to $3.3 trillion in 2021 despite shortages of processor chips for smartphones and other goods as global demand rebounded from the coronavirus pandemic. Manufacturers also were hampered by power rationing in some areas to meet government efficiency targets.

The surplus with the United States, one of the irritants behind a lingering U.S.-Chinese trade war, rose 25.1% in 2021 over a year earlier to $396.6 billion. Trade envoys have talked since President Joe Biden took office in January but have yet to announce a date to resume face-to-face negotiations.

Exports to the United States gained 27.5% over 2020 to $576.1 billion despite tariff hikes by Biden’s predecessor, Donald Trump, that still are in place on many goods. Chinese imports of American goods rose 33.1% to $179.5 billion.

In December, China’s monthly trade surplus with the United States rose 31.1% over a year earlier to $39.2 billion. Exports to the U.S. market rose 21.1% to $56.4 billion while imports of American goods edged up 3.3% to $17.1 billion.

This month, China’s global export volumes are likely to weaken due to congestion at ports where anti-coronavirus restrictions are imposed and to changes in global demand as shippers clear backlogs, said Julian Evans-Pritchard of Capital Economics.

“We’d still bet on export volumes being lower rather than higher by the end of this year,” said Evans-Pritchard in a report. Chinese imports in 2021 rose 30.1% to $2.7 trillion as the world’s second-largest recovery rebounded from the pandemic.

Economic growth weakened in the second half of the year as Beijing carried out a campaign to reduce what it sees as dangerously high debt in the real estate industry, but consumer spending was above pre-pandemic levels.

Manufacturing activity edged higher in December but new export orders contracted, according to survey earlier by the government statistics bureau and an industry group, the China Federation of Logistics & Purchasing.

Chinese exporters benefited from being allowed to resume most normal business in early 2020 while foreign competitors faced anti-coronavirus restrictions on travel and trade. That advantage carried into 2021 as other governments renewed controls in response to the spread of new virus variants.

Earlier, forecasters said Chinese exporters would benefit from the spread of the latest variant, omicron, which Beijing appeared to be keeping out of the country. More recently, however, China has responded to outbreaks within its own borders by imposing travel restrictions on major cities including Tianjin, a manufacturing center where omicron was found.