The greenback had an awful December and things may only get worse.
The currency is set to extend losses as a truce in the US-China trade war and signs that global growth is improving sap demand for haven assets, according to ABN Amro Bank.
At the same time, the US Federal Reserve has taken a dovish tilt, which will help shrink the yield premium offered by United States Treasuries, says M&G Investments.
"You had safe-haven support for the dollar in 2019, but we have a trade truce now," said ABN Amro Bank's senior foreign exchange strategist Georgette Boele in Amsterdam. "The dollar is on a path of long-term weakness."
The Bloomberg Dollar Spot Index, which tracks the US currency against 10 global peers, slid 2 per cent in December, the biggest monthly decline in almost two years.
The failure of the gauge to sustain gains made earlier last year appears to have drawn a line under a rally that saw it surge about 40 per cent from a low in 2011 to a peak in early 2017.
The US currency started to weaken from October amid signs the US and China were closing in on an initial deal to end their long-running trade dispute. The agreement was finally confirmed by President Donald Trump in December.
Another major pillar behind the dollar's multi-year advance was also undermined last year as the US central bank halted a series of rate hikes by cutting its benchmark in July, September and October to support slowing growth.
"The Fed does have some room to move lower in 2020, and for this reason I would expect a weaker dollar," said Mr Jim Leaviss, head of fixed income at M&G Investments in London. There may also be "more pressure on the Fed if growth remains mediocre going into the US elections", he added.
The Fed's dovish pivot has seen the US two-year yield advantage over similar-maturity German debt shrink to 216 basis points from around 350 basis points in late 2018, according to data compiled by Bloomberg.
"We expect to see better growth in the rest of the world ex-US," said Mr Jack McIntyre, a portfolio manager at Brandywine Global Investment Management in Philadelphia. "The primary driver of dollar weakness will be a shift in relative economic growth rates between the US and the rest of the world."
Not everyone is convinced the dollar is poised to keep weakening. Citigroup recommends betting the greenback will strengthen against the euro and Canadian dollar on a view that the US economy will outperform the rest of the world. Goldman Sachs argues the dollar will decline only if the euro and yuan appreciate significantly, and it says that looks unlikely for now.
"While we can understand the top-down logic, we are not convinced on the bottom-up case - at least over the next few months," Goldman strategists including co-head of global foreign-exchange and emerging-markets strategy Zach Pandl in New York wrote in a client note last month.