The U.S. economy is performing well but it's not immune from external challenges that could affect its success, the acting managing director of the International Monetary Fund (IMF) told CNBC Tuesday.

"No matter how you cut it, the U.S. economy is doing well and it's doing well at a time when global trade is very slow," David Lipton told CNBC's "Street Signs." But he added that there "are many events in the world that could affect the U.S. economy and it makes sense to be vigilant to all of those."

"We don't have a recession in our baseline (scenario) but in light of the trade and technology tensions, in light of the financial markets, vulnerabilities are rising," he added.

Lipton commented on the strength of the U.S. economy, noting how growth had lowered the unemployment rate to 3.7% without leading to inflation. But global trade remains a large concern for investors, business and organizations like the IMF which have highlighted the negative economic effect of barriers to trade.

U.S.- China trade tensions and the resulting tariffs have negatively affected consumers as well as many producers in both countries, the IMF's top economists said in May, warning that an increase in duties would "significantly dent business and financial market sentiment, disrupt global supply chains, and jeopardize the projected recovery in global growth in 2019."