The US state department has warned that the Gulf crisis between Qatar and its neighbours is at an impasse and could potentially drag on for weeks or even months.

The US believes the crisis could "possibly even intensify", Heather Nauert, the spokeswoman for the state department, said on Thursday.

Nauert did not specify what type of escalation the US fears, but she said Secretary of State Rex Tillerson remains in close contact with the countries involved.

"We remain very concerned about that ongoing situation between Qatar and GCC (Gulf Cooperation Council) countries," she said.

"We've become increasingly concerned that that dispute is at an impasse at this point. We believe that this could potentially drag on for weeks. It could drag on for months."

Later on Thursday, a State Department statement said Tillerson would be travelling to Kuwait on Monday to discuss efforts to resolve the Gulf crisis.

READ MORE: All the latest updates about the Gulf crisis

Saudi Arabia, Bahrain, the United Arab Emirates and Egypt cut ties to Qatar a month ago, accusing it of funding "terrorism" and spreading unrest.

Qatar has denied allegations and refused to comply in whole with a list of demands.

The White House on Thursday confirmed that President Donald Trump discussed the Qatar-Gulf crisis with German Chancellor Angela Merkel ahead of the G20 summit that starts on Friday.

In a phone conversation with Russia's Foreign Minister Sergey Lavrov on Thursday, Egypt's top diplomat Sameh Shoukry reiterated the four Arab states' "position of rejecting Qatar's support for terrorism and extremism".

Also on Thursday, Saudi Arabia accused Doha of being behind more than 23,000 Twitter accounts it blames for trying to stoke dissent in Saudi Arabia.

"We found over 23,000 Twitter accounts driven by Qatar, some of them linked to accounts calling for 'revolution' in Saudi Arabia," Saudi Information Minister Awwad Saleh al-Awwad told AFP news agency during a visit to the French capital, Paris.