President Asif Ali Zardari returned to Pakistan early Monday morning from Dubai, where he had been receiving medical treatment for a heart condition. (Ishara S. Kodikara/AFP/Getty Images)

Pakistan’s chief justice kept the pressure on President Asif Ali Zardari on Monday, demanding he respond to charges of undermining national security, in a Supreme Court inquiry into the “Memogate” controversy.

Zardari returned to Pakistan early Monday from Dubai, United Arab Emirates, where he had been receiving medical treatment for a heart condition.

His sudden departure nearly two weeks ago had sparked rumors he was fleeing the country, being ousted by the nation’s powerful military or trying to wait out the inquiry. However, his return has neither silenced the rumor mill nor ended the sense of mounting crisis surrounding his presidency.

“He will continue to face pressure from the Supreme Court and the military,” said Imtiaz Gul, executive director of the Center for Research and Security Studies in Islamabad. “The suspense will continue for quite some time.”

Zardari’s immediate troubles revolve around a secret, unsigned memo that surfaced last month, which solicited Washington’s help to rein in the Pakistani military and prevent a possible coup after the U.S. raid to kill Osama bin Laden in May.

The memo was sent by Pakistani American businessman Mansoor Ijaz, who alleged that he was following the instructions of the Pakistani ambassador to Washington to convey a message from Zardari.

The government has denied having anything to do with the memo, but the ambassador, Husain Haqqani, has resigned and is trying to clear his name.

The opposition alleged that treason had been committed, and the Supreme Court took on the inquiry, collecting depositions from government and military officials last week.

During the opening hearing Monday, Chief Justice Iftikhar Chaudhry, a longtime foe of Zardari’s, was clearly unhappy that the president had failed to respond to a request that he submit a sworn statement about the affair, saying it could be taken as acceptance of the charges.

“This is what happens in civil cases,” Chaudhry said. “When you don’t reply, then charges are deemed as accepted by you.”

Although the president can be impeached only by a two-thirds majority of parliament on the grounds of violating the constitution or gross misconduct, a Supreme Court verdict of wrongdoing in the Memogate affair would put significant pressure on Zardari.

Last week, the military appeared to be at loggerheads with the government, arguing in its depositions that evidence showed the memo did lead back to Haqqani and demanding a full investigation.

Then, over the weekend, talk surfaced in the news media that the government and military might have struck a truce.

Army chief Ashfaq Kayani met with Prime Minister Yousuf Raza Gilani for three hours Friday. Afterward the pair issued a statement calling for national unity and denying that there was any “standoff between the military and the government.”

Kayani, it emerged, had also spoken to Zardari by telephone during the meeting with Gilani, and one newspaper subsequently quoted officials as saying that the crisis had been defused and that the army did not want to bring down the government.

But Monday, those hopes were somewhat dimmed by an army statement that appeared to distance it from Zardari once again, political analysts said.

The military’s Inter-Services Public Relations division issued a terse news release saying Kayani and Zardari had spoken for about a minute, during which time the army chief had simply inquired about the president’s health. The statement said linking “some events of the last 72 hours” to this telephone conversation was “unfounded and unnecessary.”

The government’s case was significantly bolstered at the end of last week, when former U.S. national security adviser James L. Jones came to Haqqani’s defense in an affidavit, contradicting Ijaz’s story.

Jones said Ijaz, the businessman who allegedly sent the memo, had contacted him about the proposal to solicit Washington’s help to prevent a coup “a few days before May 9,” the date on which Ijaz says Haqqani had first telephoned him with the idea.

Pakistani newspapers have also begun to ask why just the government, and not the army’s spy agency, is being investigated. Ijaz had also claimed that the head of Pakistan’s military intelligence service, the ISI, had traveled to Arab countries in early May to get permission from their leaders to oust Zardari.

“In one case, the presumed culprit in Washington has been made to resign,” the Express Tribune wrote in an editorial Saturday. “In the other, the accused . . . is still in office, armed with de facto powers, along with General Kayani, to run critical areas of the country’s domestic and foreign policy.”

But even if Zadari survives the Supreme Court inquiry, his health is a matter of growing concern. His doctor in Dubai said he had sought treatment after suffering numbness and twitching in his left arm and a brief loss of consciousness. Party officials have suggested Zardari may have suffered a transient ischemic attack, a temporary interruption in blood supply to the brain that causes symptoms similar to a stroke, but no lasting damage

The 56-year-old Zardari, who suffered a heart attack in 2005, was shown on television Monday receiving a series of guests, but he looked tired.

Political analyst Gul said the possibility remained that Zardari’s opponents could try to invoke Article 47 of the constitution, which provides for the president’s removal from office “on the grounds of physical or mental incapacity.”

The Supreme Court hearing was adjourned until Thursday.

Special correspondent Shaiq Hussain contributed to this report.