Sterling was weaker across the board after Trump said on Monday the agreement allowing the United Kingdom to leave the European Union may make trade between Washington and London more difficult.

Separately, Trump told the Wall Street Journal that he expected to move ahead with raising tariffs on $200 billion in Chinese imports to 25 percent from 10 percent currently.

The threat of an escalating trade conflict between the world's two biggest economies is a major source of concern for next year, amid expectations that the world economy could slow.

The dollar index, which measures the dollar's value against six other major currencies, rose 0.2 percent to 97.28, its highest level in almost two weeks.

The greenback has advanced over the previous two sessions as investors sought the safety of the world's most liquid currency on fears that the global economic recovery was losing steam.

At the G20 meeting in Buenos Aires on Nov. 30, Trump and Chinese President Xi Jinping are expected to discuss contentious trade matters that would have an impact on trade-sensitive currencies such as the Australian and New Zealand dollars.

"The upcoming meeting between Trump and Xi is pivotal going into the year-end and for the outlook for global growth, which has shown signs of slowing," said Lee Hardman, a currency analyst at MUFG in London.

"If there's no breakthrough, that makes it more likely that more tariffs will be imposed and that increases downside risks to trade."

With the spotlight back on trade tension, the Australian dollar gave up much of its earlier gains to stand 0.1 percent up on the day at $0.7230. The New Zealand dollar was also barely higher on the day.

The euro was down 0.2 percent against the dollar at $1.1313 . The yen was steady at 113.56 yen per dollar.

Attention turned to a speech on Wednesday by Fed Chairman Jerome Powell and minutes from the central bank's Nov. 7-8 meeting to be released on Thursday, for further clues of how many more times the Fed is likely to hike interest rates.