The major stock exchange traded funds reversed premarket losses and were higher in midday trading Monday but energy sector ETFs lagged in part due to weakness in Nabors Industries (NYSE: NBR) after the company warned it sees second-quarter operating profit below expectations.

The stock was down 2% at last check. It is a top holding in sector ETFs such as PowerShares Dynamic Oil & Gas Services (NYSEArca: PXJ), Oil Service HOLDRS (AMEX: OIH) and iShares Dow Jones US Oil Equipment & Services (NYSEArca: IEZ).

Jefferies analysts said the negative preannouncement from Nabors for the second quarter was “driven largely by weather related and operational disruptions in its pressure pumping segment.”

Nabors shares fell below their 200-day moving average on Monday, a bearish technical sign.

“While the stock should take a near term hit from this news, longer term, we believe Nabors stock price is quite inexpensive at present levels and maintain our buy rating,” added analysts at Duncan-Williams in a note Monday.

PowerShares Dynamic Oil & Gas Services