The S&P 500 and Nasdaq have both felt pressure as shares of major tech companies came under pressure Monday. Investors continue to keep a close eye on rising Treasury yields, which heighten worries about valuations, particularly for some of the market's most highly valued names.

The 10-year Treasury yield ( ^TNX) added to recent gains to touch a 14-month high, trading around 4.8% as US bonds sold off. Meanwhile, the dollar ( DX-Y.NYB) surged to a two-year high against major currency peers, with the UK pound ( GBPUSD=X ), in particular, coming under pressure.