WASHINGTON: US House Speaker Nancy Pelosi insisted Friday she is not seeking to "run out the clock" on efforts by her fellow Democrats to launch impeachment proceedings against President Donald Trump before the 2020 election.

Pelosi, the top Democrat in Congress, has signalled she will only move forward with proceedings aimed at ousting the sitting president if there is overwhelming evidence of any wrongdoing and that the deeply divisive move has public support.

"No, I'm not trying to run out the clock," Pelosi told reporters as members of the House of Representatives left Washington for a six-week summer recess.

"We will proceed when we have what we need to proceed -- not one day sooner."

But she pointedly said: "This isn't endless."

Without an iron-clad case, an impeachment in the Democratic-led House will almost certainly die in the Senate, where Trump's Republicans hold a 53-47 majority.

Pelosi doubled down on her position two days after former special counsel Robert Mueller testified before Congress in a performance that Trump branded a disaster for Democrats.

But Democrats have argued that while Mueller did not provide the most camera-friendly soundbites or bombshell revelations, he brought the findings of his two-year report on Russia election interference and possible connections to the Trump campaign to a broader American audience.

Some 95 Democrats went on record last week supporting efforts to launch impeachment proceedings, and a handful more announced their backing after the Mueller report.

Pelosi was unfazed.

"I'm willing to take whatever heat there is to say, the decision will be made in a timely fashion. This isn't endless," she said.

"Their advocacy for impeachment only gives me leverage," she went on, adding: "I have no complaint with what they are doing."

Some Democrats have warned that lawmakers were running out of time to launch impeachment procedures, given that the 2020 election campaign will kick into full gear in a matter of months.

Pelosi also said she had a "good meeting" Friday with congresswoman Alexandria Ocasio-Cortez, a high-profile, first-term liberal Democrat who supports impeachment and has clashed with Pelosi on economic issues.

The speaker sought to downplay the "differences" within her party, perhaps in a bid to highlight her task of unifying the caucus as it considers its strategy against Trump in the coming months.