Hill+Knowlton Strategies is fronting China’s audacious all-cash $15.1B bid for Nexen Inc., one of Canada’s biggest energy companies, as its mounts its biggest foray into the North American market.

The acquisition bid by 70-percent-state-owned-China National Offshore Oil Corp. is bound to trigger heated political opposition in Washington over Nexen’s properties in the Gulf of Mexico.

The Democratic and Republican tandem of Bob Ludke and John Ullyot are H+K staffers who rep Cnooc in D.C. Ludke is former legislative assistant to Sen. Tom Harkin (Iowa) and senior policy analyst for the Senate Democratic Policy Committee.

Ullyot was communications director for Republican Senators John Warner (Virginia) and Arlen Specter (Penn.).

Kim Jordan of H+K’s global energy practice joins them on the account. She was Houston bureau chief for Bloomberg News.

Cnooc’s $18.5B bid in 2005 for California’s Unocal fell apart after a political uproar. The Chinese were largely interested in the southeast Asia holdings of Unocal, which was ultimately acquired by Chevron. [Public Strategies Inc., Brunswick Group and Burson-Marsteller's BKSH & Assocs. worked the Unocal bid for Cnooc.]

Cnooc CEO Li Fanrong said yesterday in Calgary that Cnooc learned valuable lessons from the Unocal failure, and noted that the current deal is a friendly acquisition that has the full support of Nexen’s board of directors.

Cnooc promises that Nexen’s U.S. assets will continue to purchase materials from local suppliers and be managed by current management.

Under the acquisition agreement, Cnooc will receive a $425M termination fee if either Nexen nixes the deal or it collapses due to regulatory pressures.

H+K’s Peter Hunt is spokesperson for Cnooc in Canada.