The Dow Jones rose by 15 points or 0.07% to 20,662.95, while the S&P 500 was at 2,357.49, up 5 points or 0.19%.

The tech-heavy Nasdaq gained 14 points or 0.25% to 5,878.95.

Earlier, new weekly US claims for jobless benefits fell to 234,000 from the previous week, down 25,000, the biggest weekly fall since April 2015.

However, shares had retreated from earlier highs by the close, with some commentators noting uncertainty among investors about President Donald Trump's meeting with Chinese Premier Xi Jinping in Florida.

The markets are particularly keen for pointers on trade relations between the world's two biggest economies.

"People are concerned because this could go south in a hurry because the Chinese president is a savvy politician with a lot of experience in these types of things and you have a novice (U.S.) politician on the world stage," said Peter Costa, president of Empire Executions Inc..

"The meeting is going to set the tone for what comes ahead and you don't want the tone to be negative," he added.

On Friday the important nonfarm payrolls figures for March will be released.

Investors will scrutinise them to try to assess whether the jobs market is robust enough to cope with the interest rate hikes which are expected in the US this year.