A Saudi-led move to isolate Qatar has had "no impact" on US military operations in the emirate, nor is any expected, a Pentagon spokesman said Tuesday.

The US has a regional command center at Al-Udeid air base near Doha from which it runs air operations throughout the region.

"There has been no impact on our operations either in Qatar or with regards to airspace permission around it and we don't anticipate there will be," Pentagon spokesman Jeff Davis said.

Bahrain, Egypt, Saudi Arabia and the United Arab Emirates severed diplomatic ties and transport links with Qatar on Monday, accusing it of supporting extremism.

US President Donald Trump threw his weight behind the effort spearheaded by Riyadh, despite Qatar's role in hosting US military operations in the fight against Islamic State extremism.

"They said they would take a hard line on funding... extremism, and all reference was pointing to Qatar. Perhaps this will be the beginning of the end to the horror of terrorism!" Trump said on Twitter.