* Mnuchin says Trump would sign McConnell stimulus deal
* U.S. ADP report shows slowing private sector hiring
* Euro hits fresh 2-1/2-year peak
* Sterling falls on negative Brexit headline
* Graphic: World FX rates in 2020 https://tmsnrt.rs/2RBWI5E (Adds Senator Schumer's comments on stimulus, updates prices)
By Gertrude Chavez-Dreyfuss and Suzanne Barlyn
NEW YORK, Dec 2 (Reuters) - The safe-haven dollar sank to a fresh 2-1/2-year low in choppy trading on Wednesday, pressured once again by expectations of further fiscal stimulus for the United States.
The dollar, however, last traded little changed on the day amid wrangling in Congress over additional coronavirus aid.
U.S. Senate Democratic Leader Chuck Schumer on Wednesday rejected the latest Republican coronavirus aid plan. He described it as an "inadequate, partisan proposal" that would help shield businesses from liability lawsuits but fail to help workers hurt by the pandemic.
That came a day after a proposed bipartisan coronavirus pandemic-related economic stimulus package on Tuesday worth $908 billion lifted the market's appetite for risk and pushed the dollar to its lowest level since April 2018.
That trend continued on Wednesday, after U.S. Treasury Secretary Steven Mnuchin said Republican President Donald Trump would sign a pandemic relief deal proposed by Senate Majority Leader Mitch McConnell.
For months, Republican McConnell has pushed for a $500 billion plan that Democrats rejected as insufficient.
Vassili Serebriakov, an FX strategist at UBS in New York said the momentum for a weaker dollar should continue. "Any bounces in the dollar are likely to find sellers."
In midday trading, the dollar index, which measures the greenback against a basket of major currencies, was flat to slightly lower at 91.146, after hitting 91.100 overnight, the lowest level since late April 2018.
Wednesday's data showing slower U.S. private hiring last month supported some safe-haven buying of the dollar earlier in the session.
Private payrolls increased by 307,000 jobs in November, the ADP National Employment Report showed, lower than economists' forecast for a 410,000 rise in new jobs. Data for October, though, was revised up to show 404,000 jobs added instead of the initially reported 365,000.
Britain's approval of a COVID-19 vaccine and the possibility that U.S. unemployment data will help spur a pandemic relief package in Washington are likely to support investors' risk tolerance, driving them away from the dollar, UBS' Serebriakov said.
The UK approved Pfizer Inc's COVID-19 vaccine on Wednesday, jumping ahead of the rest of the world in the race to begin the most crucial mass inoculation program in history.
The euro, meanwhile, was up 0.2% at $1.2094, after earlier hitting $1.2108, the highest since late April 2018.
The European Central Bank meets next week and analysts said the ECB could act to stem the euro's rapid rise.
Against the yen, the dollar rose 0.2% to 104.47, after the Bank of Japan signaled its readiness to extend pandemic-response programs.
Bitcoin was up 1% at $18,978 , after hitting a record high of $19,918.01 on Tuesday.
Sterling fell as Britain and the European Union quickly approached a make-or-break moment in trade talks, with many investors doubting a deal will be reached.
The pound last traded down 0.5% against the dollar at $1.3361.
The risk-sensitive Aussie dollar rose 0.4% versus the greenback to US$0.74. It bounced in Asia as data showed Australia's economy rebounded more than expected in the third quarter. (Reporting by Gertrude Chavez-Dreyfuss and Suzanne Barlyn; Editing by Will Dunham and Jonathan Oatis)