The main issue is the deadlock between Congressional Democrats and Republicans over healthcare funding, and neither side is willing to cave.

WASHINGTON, Oct. 15 (Xinhua) -- The U.S. government's partial shutdown has hit day 14 on Tuesday, with no signs of abating.

The main issue is the deadlock between Congressional Democrats and Republicans over healthcare funding, and neither side is willing to cave.

The Senate on Tuesday rejected a GOP House-passed short-term funding bill to reopen the government for the eighth time, ensuring the shutdown enters its third week. The bill needed 60 votes to advance but merely received 49.

House Speaker Mike Johnson, a Republican from Louisiana, warned of the possible impacts of a prolonged shutdown.

"We're barreling toward one of the longest shutdowns in American history, unless Democrats drop their partisan demands and pass a clean, no-strings-attached budget to reopen the government and pay our federal workers," he said on Monday.

Democrats, in turn, accuse Republicans of wanting to cut crucial healthcare funding for the American people.

The lengthiest U.S. government shutdown ever recorded lasted 35 days during President Donald Trump's first term, in late 2018 and early 2019.

Republican members of Congress claim that Democrats want to extend the shutdown beyond the scheduled protests this weekend in Washington, in an attempt to show party activists that they are pushing back against the Trump administration.

More than 4,000 federal employees received layoff notices, according to a court filing last Friday. The White House on Monday said the administration plans to continue mass firing of the federal workforce as the shutdown continues.

In a statement on social media, the Office of Management and Budget wrote it is "making every preparation to batten down the hatches and ride out the Democrats' intransigence."

"Pay the troops, pay law enforcement, continue the RIFs, and wait," the office added. RIF denotes "reduction in force", or scaling down of the workforce.

Brookings Institution Senior Fellow Darrell West told Xinhua: "The shutdown is starting to affect the economy and slow economic growth. It is also delaying the publication of important government reports."

"The shutdown weakens global opinion towards the United States and makes it look like our leaders are incompetent. Other nations will argue America does not know how to govern itself," West said.

Dean Baker, co-founder of the Center for Economic and Policy Research, told Xinhua: "The impact has for the most part been limited, but it is about to increase."

"Some government offices have been shut ... Many national parks and museums are closed. The biggest impact has probably been on air traffic. Many controllers, working without pay, are calling in sick," Baker said.

"This can cascade because we already had a serious shortage. Overworked controllers may literally feel they can't deal with the load. Many flights have already been cancelled or delayed," Baker added.

Some believe the shutdown could backfire on the White House.

Christopher Galdieri, a political science professor at Saint Anselm College in the northeastern state of New Hampshire, told Xinhua: "This is putting government dysfunction front and center for many Americans who otherwise might not spend much time thinking about politics."

"Secondly, it's stepping on otherwise good news for the administration," Galdieri said, referring to the Gaza peace deal that Trump brokered in recent days.

One important impact receiving less attention is the freezing of the U.S. research and development sector, said Clay Ramsay, a researcher at the Center for International and Security Studies at the University of Maryland.

These activities take place within government agencies and their contractors and within universities, Ramsay noted.

"These domains are interactive, so in a government shutdown, the different parts gradually come to a stop. For example, currently, NASA is almost entirely shut down," Ramsay said.

"This also affects America's place in international science, with a growing perception that U.S. standards are dropping and that it is not the best country to go to for a scientific career," Ramsay said.