Aug 21 (Reuters) - U.S. oil and gas producer

ConocoPhillips ( COP ) said on Thursday it would secure 4

million tonnes per annum of liquefied natural gas from Sempra's ( SRE )

Port Arthur LNG Phase 2 project in Texas to serve key

global markets.

ConocoPhillips ( COP ) will buy LNG over a 20-year term on a

free-on-board basis, the company said in a statement.

The deal extends the U.S. oil producer's partnership with

Sempra ( SRE ), where ConocoPhillips ( COP ) already holds a 30% equity stake in

Phase 1 of the Port Arthur LNG project.

Phase 1 is under construction and expected to start

operations in 2027.