(Updates with index/price moves and geopolitical news from the first paragraph.)

US equity indexes were mixed in midday trading on Monday amid gains in government bond yields and higher crude oil prices.

The Nasdaq Composite slipped 0.2% to 26,637.2, with the Dow Jones Industrial Average down 0.2% to 53,941.2. The S&P 500 was little changed at 7,758.9.

President Donald Trump signaled a US emphasis on increasing economic pressure on Iran, saying that Washington is "low-keying" negotiations with the country, CNN reported.

Iran said it was nearing a final pact with Oman to define new shipping lanes between them through the Strait of Hormuz, but reiterated that the US must meet other conditions, including compensation and an end to sanctions and military threats, before the waterway is reopened, Reuters reported.

The front-month US West Texas Intermediate crude oil contract jumped 3.5% to $80.88 a barrel, and global benchmark North Sea Brent advanced 3.4% to $86.40 a barrel.

US Treasury yields rose, with the 10-year yield up 3.6 basis points to 4.69% and the two-year higher by 3.3 basis points to 4.24%.