Saudi Arabia's King Salman will not attend today’s Gulf Co-operation Council (GCC) summit in Kuwait.
King Salman has sent his foreign minister Adel Al Jubeir to head the delegation.
Bahrain has sent its Deputy Prime Minister Shaikh Mohammed bin Mubarak Al Khalifa to head its delegation, while Emirati media reported that the state minister for foreign affairs would represent Abu Dhabi.
All three Gulf states, along with Egypt, cut ties with Qatar on June 5, accusing it of supporting extremists.
Kuwait has been leading mediation efforts within the GCC to resolve the crisis, but so far with little success.
Meanwhile, UAE said on Tuesday it was forming a new military and economic committee with Saudi Arabia separate from the GCC.
The committee "will co-ordinate between the two countries in all military, political, economic, trade and cultural fields", according to a decree issued by UAE President Sheikh Khalifa bin Zayed Al Nahyan.
Bahrain in October called for Qatar's membership of the GCC to be suspended until it accepted the demands of the four boycotting countries.