Story highlights House Speaker Paul Ryan spoke to his fellow Republicans on a conference call Monday morning

The Wisconsin Republican said he'll focus solely on keeping Congress under GOP control

Washington (CNN) House Speaker Paul Ryan dealt his own party's presidential nominee a withering blow Monday, telling fellow Republicans he will no longer defend Donald Trump and will instead use the next 29 days to focus on preserving his party's hold on Congress.

"The speaker is going to spend the next month focused entirely on protecting our congressional majorities," Ryan's spokeswoman, AshLee Strong, said in a statement.

The move -- highly unusual in US political history -- laid bare the seemingly intractable divisions now seizing the Republican Party with a month left before the presidential vote. Support for Trump among the GOP establishment, already weak amid disagreements over policy and tone, has now eroded to new lows.

In a conference call with members Monday morning, Ryan told lawmakers, "you all need to do what's best for you and your district," according to someone who listened to the meeting.

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