Qatar Petroleum (QP) is looking to invest at least $20 billion in the United States over the coming few years, its chief executive told Reuters, after the Gulf Arab state quit OPEC, freeing Doha from potential legal risks in the United States.

Saad al-Kaabi, who holds the energy portfolio of the world's top liquefied natural gas (LNG) producer, also said on Sunday QP aimed to announce its foreign partners for the new LNG trains it is building by the middle of next year.

But he added QP could carry out the project alone, with no international oil company at its side, if no good offers were made.

"Mark my words, if I don't get a good deal, we go alone," Kaabi said in an interview at his office in Doha.