Washington (CNN) The US ambassador to Mexico has announced that she is stepping down in May.

Roberta Jacobson made the announcement in a tweet in Spanish on Thursday, "I will be departing at the beginning of May, in search of other opportunities."

The resignation comes at a time when US relations with Mexico have been strained over issues related to trade and migration and, Jacobson ended her tweet stating, "We are Stronger Together!"

"I do it knowing the US-Mexico relationship is strong and vital and that this amazing Mission Mexico team will continue to ensure it remains so," she adds. "At this time, I have no news to share on my successor."

A source close to Jacobson said, "it was a tough job and she is looking for new opportunities outside government after 31 years."

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