Cleary Gottlieb and Shearman & Sterling are lead advisers on a deal in which Mexican state oil company Petróleos Mexicanos (Pemex) has secured a $5 billion cash injection from the government, as part of a broader refinancing effort as it struggles to service an unwieldy debt load.

Cleary is representing Pemex and the Mexican Finance Ministry, both longtime clients of the firm, in what it described on Wednesday as a series of “landmark” liability management transactions intended to strengthen Pemex’s finances.