WASHINGTON (Reuters) - U.S. small-business confidence surged to the highest level in just over six years in December, extending post election gains. 

The National Federation of Independent Business said on Tuesday its Small Business Optimism Index increased 3.4 points to 105.1 last month, the highest reading since October 2018.

It was the second straight month that the index pushed past the 51-year average of 98. The survey's Uncertainty Index dropped 12 points to 86. The Nov. 5 U.S. election gave Republicans control of the White House and the U.S. Congress. Small business owners tend to lean Republican. 

Though other sentiment surveys also perked up in the aftermath of the election, caution is setting in among consumers amid concerns that broad tariffs on imports and mass deportations of undocumented immigrants pledged by President-elect Donald Trump's incoming administration could raise prices for households. 

The University of Michigan's survey last Friday showed both one-year and long-run inflation expectations soared in January, with its consumer sentiment index dipping. 

The share of small business owners expecting the economy to improve increased 16 points to 52% in December, the highest level since the fourth quarter of 1983. The proportion saying now is a good time to expand their business was the highest since February 2020. More small business owners expected growth in inflation-adjusted sales.