Law enforcement in major U.S. cities, including New York City and Washington, D.C., have ramped up security this week.

WASHINGTON, March 22 (Xinhua) -- The United States has been put on edge over the possibility that former President Donald Trump would be indicted over an alleged hush-money payment during his 2016 election campaign.

Law enforcement in major U.S. cities, including New York City and Washington, D.C., have ramped up security this week.

"While law enforcement is not tracking any specific, credible threats against the Capitol or state offices, there is potential for demonstration activity," the Senate sergeant at arms recently wrote in a notice to the offices of U.S. senators.

Capitol Police are "working with law enforcement partners, so you may observe a greater law enforcement presence on Capitol Hill," the notice obtained by U.S. media outlets read.

Bike racks were set up along some streets near the Capitol, located on Capitol Hill at the eastern end of the National Mall in Washington, D.C. Authorities have also erected metal barricades outside the district attorney's office and the criminal court in Manhattan, New York City.

Trump wrote on his Truth Social platform over the weekend that he expected to be arrested this week in connection to the Manhattan district attorney's office's probe into the 2016 payment made to American adult film actress Stormy Daniels. In the post, Trump urged his supporters to "protest, take our nation back!"

Joe Tacopina, Trump's attorney, warned that it would be "an all-out war" if Trump, who's seeking the White House again in 2024, is indicted. U.S. Senator Lindsey Graham, a South Carolina Republican, also suggested that bringing charges against Trump would "blow up our country."

The investigation is examining Trump's involvement in the payment of 130,000 U.S. dollars to Daniels in order to keep her quiet about an alleged sexual encounter she said she had with him in 2006.

Then-Trump attorney Michael Cohen paid Daniels, whose real name is Stephanie Clifford, before being reimbursed by the Trump Organization, which described the reimbursement as legal fees.

Trump has denied wrongdoing and that the affair happened, while charging that the inquiry led by Manhattan District Attorney Alvin Bragg, a Democrat, is politically motivated.

The possible indictment of Trump has been closely watched as no former U.S. president has been indicted on criminal charges.

A Manhattan grand jury, which was previously scheduled to hear from at least one more witness on Wednesday before any charges are filed, would not meet Wednesday, U.S. media reported.

Bragg is likely to work with Trump's team to arrange his surrender in New York City if he is indicted. Trump lives in his Mar-a-Lago resort in Florida, and Tacopina has said that the Republican, who served as U.S. president from January 2017 to January 2021, would not refuse to surrender.

Trump would have to be arraigned in New York City but the 2024 presidential candidate is expected to continue campaigning since he is unlikely to be held in Manhattan while the case against him plays out.

In addition to the hush-money payment case, Trump is facing several other criminal investigations at the state and federal level, including his efforts to overturn his 2020 election loss, his handling of classified documents, and his role in the Jan. 6, 2021, Capitol riot.