Mexico City - New U.S. Ambassador to Mexico Christopher Landau arrived in Mexico City on Friday to take up one of Washington’s most important diplomatic posts, which had been empty for over a year.

Landau replaces Roberta Jacobson, the first woman to be the United States’ envoy to Mexico. She resigned and retired in May 2018.

The North American neighbors are key commercial partners but Landau’s arrival comes after months of tensions over immigration and trade.

Mexico has cracked down on migrants and asylum seekers moving through its territory after U.S. President Donald Trump threatened to slap tariffs on imports from Mexico. The two governments are hoping for ratification of a trade deal with Canada that replaced the North American Free Trade Agreement.

Landau is a Harvard-educated lawyer who has argued nine cases before the Supreme Court and who clerked for Justices Antonin Scalia and Clarence Thomas in the early 1990s.

On arriving in Mexico City, Landau told journalists at the airport that Mexico and the United States face “challenges” just as in all close relationships.

The countries are “partners, neighbors and friends,” Landau said.

“I come with my hand extended,” he added.

He is married and has two children.