Vice President Mike Pence will push back a planned Middle East trip as the Senate tries to pass a bill that would overhaul the U.S. tax system, his office said Thursday.

If two of the 52 Senate Republicans oppose the tax plan in a vote expected by Tuesday, Pence would need to break a tie for the legislation to pass. He is now expected to leave the United States on Tuesday, rather than a planned Saturday departure date.

"Yesterday the White House informed Senate leadership that due to the historic nature of the vote in the Senate on tax cuts for millions of Americans, the vice president would stay to preside over the vote," Pence's press secretary, Alyssa Farah, said in a statement. "The vice president will then travel to Egypt and Israel where he'll reaffirm the United States' commitment to its allies in the Middle East and to working cooperatively to defeat radicalism."

Republicans do not expect to need Pence's vote, but he wants to see the legislation through its passage, a White House official told NBC News.

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Last week, Palestinian Authority President Mahmoud Abbas said he would not meet with Pence over the Trump administration's recognition of Jerusalem as Israel's capital. The White House insists the delay has nothing to do with Abbas' decision, according to NBC.

Pence plans to travel to Egypt and Israel.

Republicans believe they have the votes to pass their tax proposal next week. However, possible opposition from some GOP senators, as well as health problems faced by two others, has thrown some uncertainty into the process.

It is unclear currently how Republican Sens. Bob Corker of Tennessee, Susan Collins of Maine and potentially some others will vote on the GOP legislation. Corker was the only Republican to oppose a Senate version of the bill.

Meanwhile, GOP Sens. John McCain of Arizona and Thad Cochran of Mississippi have missed votes this week due to health problems. McCain is undergoing treatments related to brain cancer.

Cochran reportedly had a nonmelanoma lesion removed from his nose but is available for votes next week.